# data[].attributes.body
it's mexico

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TORII, 大町-1144 Miyajimacho, Hatsukaichi, Hiroshima, Japan

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TORII, 大町-1144 Miyajimacho, Hatsukaichi, Hiroshima, Japan

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TORII, 大町-1144 Miyajimacho, Hatsukaichi, Hiroshima, Japan

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Taj Mahal, Dharmapuri, Forest Colony, Tajganj, Agra, Uttar Pradesh, India

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Taj Mahal, Dharmapuri, Forest Colony, Tajganj, Agra, Uttar Pradesh, India

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Taj Mahal, Dharmapuri, Forest Colony, Tajganj, Agra, Uttar Pradesh, India

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The (レインボーブリッジ, Rainbow Bridge Reinbō Burijji) is a suspension bridge crossing northern Tokyo Bay between Shibaura Pier and the Odaiba waterfront development in Minato, Tokyo, Japan.

It was built by Kawasaki Heavy Industries, with construction starting in 1987 and completed in 1993. The bridge is 798 metres (2,618 ft) long with a main span of 580 metres (1,903 ft). Officially called the " Shuto Expressway No. 11 Daiba Route - Port of Tokyo Connector Bridge," the name "'Rainbow Bridge" was decided by the public.

The towers supporting the bridge are white in color, designed to harmonize with the skyline of central Tokyo seen from Odaiba. There are lamps placed on the wires supporting the bridge, which are illuminated into three different colors, red, white and green every night using solar energy obtained during the day.

The bridge can be accessed by foot from Tamachi Station ( JR East) or Shibaura-futō Station ( Yurikamome) on the mainland side.

The Rainbow Bridge carries three transportation lines on two decks. The upper deck carries the Shuto Expressway's Daiba Route, while the lower deck carries the Yurikamome rapid transit system in the centre, walkways on the outer side, and Tokyo Prefectural Route 482 in-between. Route 482 was formerly a tolled road, but opposition to the toll led to its removal.[citation needed ] Light motorcycles under 50cc are not permitted on either deck or the walkway of the bridge. Motorcycle pillion passengers are also banned.

The bridge has two separate walkways on the north and south sides of the lower deck; the north side offers views of the inner Tokyo harbour and Tokyo Tower, while the south side offers views of Tokyo Bay and occasionally Mount Fuji. The walkways may only be used during certain hours (9 am to 9 pm in the summer; 10 am to 6 pm in the winter, access to the walkways close 30 minutes before closing time.) Bicycles are permitted on the condition that they are pushed (as opposed to riding them).

# data[].attributes.attachment_link.description
The (レインボーブリッジ, Rainbow Bridge Reinbō Burijji) is a suspension bridge crossing northern Tokyo Bay between Shibaura Pier and the Odaiba waterfront development in Minato, Tokyo, Japan. It was built by Kawasaki Heavy Industries, with construction starting in 1987 and completed in 1993.

# data[].attributes.location_name
Rainbow Bridge, 33, Minato City, Tokyo, Japan

# data[].attributes.headline
Rainbow Bridge, 33, Minato City, Tokyo, Japan

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Rainbow Bridge, 33, Minato City, Tokyo, Japan

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https://en.wikipedia.org/wiki/Rainbow_Bridge_(Tokyo)

# data[].attributes.attachment_link.readable_text
The (レインボーブリッジ, Rainbow Bridge Reinbō Burijji) is a suspension bridge crossing northern Tokyo Bay between Shibaura Pier and the Odaiba waterfront development in Minato, Tokyo, Japan.

It was built by Kawasaki Heavy Industries, with construction starting in 1987 and completed in 1993. The bridge is 798 metres (2,618 ft) long with a main span of 580 metres (1,903 ft). Officially called the " Shuto Expressway No. 11 Daiba Route - Port of Tokyo Connector Bridge," the name "'Rainbow Bridge" was decided by the public.

The towers supporting the bridge are white in color, designed to harmonize with the skyline of central Tokyo seen from Odaiba. There are lamps placed on the wires supporting the bridge, which are illuminated into three different colors, red, white and green every night using solar energy obtained during the day.

The bridge can be accessed by foot from Tamachi Station ( JR East) or Shibaura-futō Station ( Yurikamome) on the mainland side.

The Rainbow Bridge carries three transportation lines on two decks. The upper deck carries the Shuto Expressway's Daiba Route, while the lower deck carries the Yurikamome rapid transit system in the centre, walkways on the outer side, and Tokyo Prefectural Route 482 in-between. Route 482 was formerly a tolled road, but opposition to the toll led to its removal.[citation needed ] Light motorcycles under 50cc are not permitted on either deck or the walkway of the bridge. Motorcycle pillion passengers are also banned.

The bridge has two separate walkways on the north and south sides of the lower deck; the north side offers views of the inner Tokyo harbour and Tokyo Tower, while the south side offers views of Tokyo Bay and occasionally Mount Fuji. The walkways may only be used during certain hours (9 am to 9 pm in the summer; 10 am to 6 pm in the winter, access to the walkways close 30 minutes before closing time.) Bicycles are permitted on the condition that they are pushed (as opposed to riding them).

# data[].attributes.attachment_link.description
The (レインボーブリッジ, Rainbow Bridge Reinbō Burijji) is a suspension bridge crossing northern Tokyo Bay between Shibaura Pier and the Odaiba waterfront development in Minato, Tokyo, Japan. It was built by Kawasaki Heavy Industries, with construction starting in 1987 and completed in 1993.

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Washington Monument, Washington, DC, USA

# data[].attributes.headline
Washington Monument, Washington, DC, USA

# data[].attributes.subject
Washington Monument, Washington, DC, USA

# data[].attributes.attachment_link.readable_text
The Washington Monument is an obelisk shaped building within the National Mall in Washington, D.C., built to commemorate George Washington, once commander-in-chief of the Continental Army (1775-1784) in the American Revolutionary War and the first President of the United States (1789-1797). Located almost due east of the Reflecting Pool and the Lincoln Memorial, the monument, made of marble, granite, and bluestone gneiss, is both the world's tallest predominantly stone structure and the world's tallest obelisk, standing 554 feet inches (169.046 m) tall according to the U.S. National Geodetic Survey (measured 2013-14) or 555 feet inches (169.294 m) tall, according to the National Park Service (measured 1884). It is the tallest monumental column in the world if all are measured above their pedestrian entrances. It was the tallest structure in the world between 1884 and 1889, after which it was overtaken by the Eiffel Tower in Paris. Previously, the tallest structure was the Cologne Cathedral.

Construction of the presidential memorial began in 1848 and was halted for a period of 23 years, from 1854 to 1877 due to a lack of funds, a struggle for control over the Washington National Monument Society, and the American Civil War. Although the stone structure was completed in 1884, internal ironwork, the knoll, and installation of memorial stones were not completed until 1888. A difference in shading of the marble, visible approximately 150 feet (46 m) or 27% up, shows where construction was halted and later resumed with marble from a different source. The original design was by Robert Mills (1781-1855) of South Carolina, but he did not include his proposed colonnade due to a lack of funds, proceeding only with a bare obelisk. The cornerstone was laid on July 4, 1848; the first stone was laid atop the unfinished stump on August 7, 1880; the capstone was set on December 6, 1884; the completed monument was dedicated on February 21, 1885; and officially opened October 9, 1888.

The Washington Monument is a hollow Egyptian style stone obelisk with a 500-foot (152.4 m) tall column surmounted by a 55-foot (16.8 m) tall pyramidion. Its walls are 15 feet (4.6 m) thick at its base and feet (0.46 m) thick at their top. The marble pyramidion has thin walls only 7 inches (18 cm) thick supported by six arches, two between opposite walls that cross at the center of the pyramidion and four smaller corner arches. The top of the pyramidion is a large marble capstone with a small aluminum pyramid at its apex with inscriptions on all four sides. The lowest 150 feet (45.7 m) of the walls, constructed during the first phase 1848-1854, are composed of a pile of bluestone gneiss rubble stones (not finished stones) held together by a large amount of mortar with a facade of semi-finished marble stones about feet (0.4 m) thick. The upper 350 feet (106.7 m) of the walls, constructed during the second phase 1880-1884, are composed of finished marble surface stones, half of which project into the walls, partially backed by finished granite stones.

The interior is occupied by iron stairs that spiral up the walls, with an elevator in the center, each supported by four iron columns, which do not support the stone structure. The stairs contain fifty sections, most on the north and south walls, with many long landings stretching between them along the east and west walls. These landings allowed many inscribed memorial stones of various materials and sizes to be easily viewed while the stairs were accessible (until 1976), plus one memorial stone between stairs that is difficult to view. The pyramidion has eight observation windows, two per side, and eight red aircraft warning lights, two per side. Two aluminum lightning rods, connected via the elevator support columns to ground water, protect the monument. The monument's present foundation is 37 feet (11.3 m) thick, consisting of half of its original bluestone gneiss rubble encased in concrete. At the northeast corner of the foundation, 21 feet (6.4 m) below ground, is the marble cornerstone, including a zinc case filled with memorabilia. Fifty American flags fly on a large circle of poles centered on the monument. In 2001, a temporary screening facility was added to the entrance to prevent a terrorist attack. An earthquake in 2011 slightly damaged the monument, and it was closed until 2014. It was closed again for elevator system repairs, security upgrades, and mitigation of soil contamination from August 2016 to September 2019.

George Washington (1732-1799), hailed as the father of his country, and as the leader who was "first in war, first in peace and first in the hearts of his countrymen" (in eulogy by Maj. Gen. 'Light-Horse Harry' Lee at Washington's funeral, December 26, 1799), was the dominant military and political leader of the new United States of America from 1775 to 1799. Even his former enemy King George III called him "the greatest character of the age".

At his death in 1799, he left a critical legacy: Washington was the unchallenged public icon of American military and civic patriotism. He was also identified with the Federalist Party, which lost control of the national government in 1800 to the Jeffersonian Republicans, who were reluctant to celebrate the hero of the opposition party.

Starting with victory in the Revolution, there were many proposals to build a monument to Washington, beginning with an authorization in 1783 by the old Confederation Congress to erect an equestrian statue of the General in a future American national capital city. After his December 1799 death, the United States Congress authorized a suitable memorial in the planned national capital then under construction since 1791, but the decision was reversed when the Democratic-Republican Party (Jeffersonian Republicans) took control of Congress in 1801 after the pivotal 1800 Election, with the first change of power between opposing political parties. The Republicans were dismayed that Washington had become the symbol of the Federalist Party; furthermore the values of Republicanism seemed hostile to the idea of building monuments to powerful men. They also blocked his image on coins or the celebration of his birthday. Further political squabbling, along with the North-South division on the Civil War, blocked the completion of the Washington Monument until the late 19th century. By that time, Washington had the image of a national hero who could be celebrated by both North and South, and memorials to him were no longer controversial.

As early as 1783, the old Confederation Congress (successors after 1781 to the earlier Second Continental Congress) had resolved "That an equestrian statue of George Washington be erected at the place where the residence of Congress shall be established". The proposal called for engraving on the statue which explained it had been erected "in honor of George Washington, the illustrious Commander-in-Chief of the Armies of the United States of America during the war which vindicated and secured their liberty, sovereignty, and independence". Currently, there are two equestrian statues of President Washington in the national capital city of Washington, D.C. One is located in Washington Circle at the intersection of the Foggy Bottom and West End neighborhoods at the north end of the George Washington University campus, and the other is in the gardens of the National Cathedral of the Episcopal Church on Mount St. Alban in northwest Washington.

On December 24, 1799, 10 days after Washington's death, a U.S. Congressional committee recommended a different type of monument. John Marshall (1755-1835), a Representative from Virginia (who later became Chief Justice of the United States, 1801-1835) proposed that a tomb be erected within the Capitol and it was designed later to place such a crypt sepulchre below the rotunda of the great dome. However, a lack of funds, disagreement over what type of memorial would best honor the country's first president, and the Washington family's reluctance to move his body from Mount Vernon prevented progress on any project.

Progress toward a memorial finally began in 1833. That year a large group of citizens formed the Washington National Monument Society. Three years later, in 1836, after they had raised $28,000 in donations (equivalent to $1,000,000 in 2020), they announced a competition for the design of the memorial.

On September 23, 1835, the board of managers of the society described their expectations:

It is proposed that the contemplated monument shall be like him in whose honor it is to be constructed, unparalleled in the world, and commensurate with the gratitude, liberality, and patriotism of the people by whom it is to be erected ... [It] should blend stupendousness with elegance, and be of such magnitude and beauty as to be an object of pride to the American people, and of admiration to all who see it. Its material is intended to be wholly American, and to be of marble and granite brought from each state, that each state may participate in the glory of contributing material as well as in funds to its construction.

The society held a competition for designs in 1836. In 1845, the winner was announced to be architect Robert Mills, supposedly the first native-born American to be professionally trained as an architect. The citizens of Baltimore had chosen him in 1814 to build one of the first monuments to George Washington originally planned for the former courthouse square in their port city, and he had designed a tall elaborately decorated Greek column with balconies, surmounted by a statue of the President. Mills' Baltimore monument, with cornerstone laid and construction begun in 1815, was later simplified to a plain column shaft with a statue of a toga-clad Washington at the top when it was completed in 1829, but moved (because of its height) to the then rural hills to the north, where the city's growth would later extend. Mills also knew the capital well, with its being only 40 miles (65 kilometers) southwest of Baltimore, and his having just been chosen Architect of Public Buildings for Washington. His design called for a circular colonnaded building 250 feet (76 m) in diameter and 100 feet (30 m) high from which sprang a four-sided obelisk 500 feet (150 m) high, for a total elevation of 600 feet (180 m). A massive cylindrical pillar 70 feet (21 m) in diameter supported the obelisk at the center of the building. The obelisk was to be 70 feet (21 m) square at the base and 40 feet (12 m) square at the top with a slightly peaked roof. Both the obelisk and pillar were hollow within which a railway spiraled up. The obelisk had no doorway-instead its interior was entered from the interior of the pillar upon which it was mounted. The pillar had an "arched way" at its base. The top of the portico of the building would feature Washington standing in a chariot holding the reins of six horses. Inside the colonnade would be statues of 30 prominent Revolutionary War heroes as well as statues of the 56 signers of the Declaration of Independence.

Criticism of Mills's design and its estimated price tag of more than $1 million (in 1848 money, equivalent to $20,000,000 in 2020) caused the society to hesitate. On April 11, 1848, the society decided, due to a lack of funds, to build only a simple plain obelisk. Mills's 1848 obelisk was to be 500 feet (150 m) tall, 55 feet (17 m) square at the base and 35 feet (11 m) square at the top. It had two massive doorways, each 15 feet (4.6 m) high and 6 feet (1.8 m) wide, on the east and west sides of its base. Surrounding each doorway were raised jambs, a heavy pediment, and entablature within which was carved an Egyptian-style winged sun and asps. Some of these details can be seen in the 1860 photograph below at Donations run out, after clicking on the image and viewing the original file at its highest magnification. This original design conformed to a massive temple which was to have surrounded the base of the obelisk, but because it was never built, the architect of the second phase of construction Thomas Lincoln Casey smoothed down the projecting jambs, pediment and entablature in 1885, walled up the west entrance with marble forming an alcove, and reduced the east entrance to 8 feet (2.4 m) high. The western alcove has contained a bronze statue of Washington since 1992-93. Also during 1992-93 a limestone surround was installed at the east elevator entrance decorated with a winged sun and asps to mimic Mills's 1848 design.

The Washington Monument was originally intended to be located at the point at which a line running directly south from the center of the White House crossed a line running directly west from the center of the U.S. Capitol on Capitol Hill. French born and military engineer Pierre (Peter) Charles L'Enfant's 1791 visionary "Plan of the city intended for the permanent seat of the government of the United States ..." designated this point as the location of the proposed central equestrian statue of George Washington that the old Confederation Congress had voted for in 1783, at the end of the American Revolutionary War (1775-1783) in a future American national capital city. The ground at the intended location proved to be too unstable to support a structure as heavy as the planned obelisk, so the monument's location was moved 390 feet (118.9 m) east-southeast. At that originally intended site there now stands a small monolith called the Jefferson Pier. This offset caused the McMillan Plan to specify that the Lincoln Memorial should be "placed on the main axis of the Capitol and the Monument", about 1° south of due west of the Capitol or the monument, not due west of the Capitol or the monument.

Gordon's arguments are valid for the second phase (1879-1888) after slavery was abolished, when every stone laid required dressing and polishing by a skilled stonemason. This includes the iron staircase which was constructed 1885-86. That the stonecutters in the quarry were slaves is confirmed because all quarry workers were slaves during the construction of the United States Capitol during the 1790s. However, Holland's views are valid for the first phase because most of its construction only required unskilled manual labor. No information survives concerning the method used to lift stones that weighed several tons each during the first phase, whether by a manual winch or a steam engine. The surviving information concerning slaves that built the core of the United States Capitol during the 1790s is not much help. At the time, the District of Columbia outside of Georgetown was sparsely populated so the federal government rented slaves from their owners who were paid a fee for their slaves' normal daily labor. Any overtime for Sundays, holidays, and nights was paid directly to the slaves which they could use for daily needs or to save to buy their freedom. Conversely, the first phase of the monument was constructed by a private entity, the Washington National Monument Society, which may not have been as magnanimous as the federal government, but most information was lost during the 1850s while two Societies vied for control of the monument. Useful information concerning the use of slaves during the major expansion of the Capitol during the 1850s, nearly contemporaneous with the monument's first phase, does not exist.

Only a small number of stones used in the first phase required a skilled stonemason, the marble blocks on the outer surface of the monument (their inner surfaces were left very rough) and those gneiss stones that form the rough inner walls of the monument (all other surfaces of those inner stones within the walls were left jagged). The vast majority of all gneiss stones laid during the first phase, those between the outer and inner surfaces of the walls, from very large to very small jagged stones, form a pile of rubble held together by a large amount of mortar. The top surface of this rubble can be seen below at Walls in an 1880 drawing made just before the polished/rough marble and granite stones used in the second phase were laid atop it. The original foundation below the walls was made of layered gneiss rubble, but without the massive stones used within the walls. Most of the gneiss stones used during the first phase were obtained from quarries in the upper Potomac River Valley. Almost all the marble stones of the first and second phases came from two Maryland quarries about 20 miles (30 km) north of downtown Baltimore in rural Baltimore County where stone for their first Washington Monument was obtained.[citation needed ]

On Independence Day, July 4, 1848, the Freemasons, the same organization to which Washington belonged, laid the cornerstone (symbolically, not physically).: 45, 136-143  According to Joseph R. Chandler:: 136, 140-141

No more Washingtons shall come in our time ... But his virtues are stamped on the heart of mankind. He who is great in the battlefield looks upward to the generalship of Washington. He who grows wise in counsel feels that he is imitating Washington. He who can resign power against the wishes of a people, has in his eye the bright example of Washington.

Two years later, on a torrid July 4, 1850, George Washington Parke Custis (1781-1857), the adopted son of George Washington and grandson of Martha Washington (1731-1802), dedicated a stone from the people of the District of Columbia to the Monument at a ceremony that 12th President Zachary Taylor (1784-1850, served 1849-1850) attended, just five days before he died from food poisoning.

Construction continued until 1854, when donations ran out and the monument had reached a height of 152 feet (46.3 m). At that time a memorial stone that was contributed by Pope Pius IX, called the Pope's Stone, was destroyed by members of the anti-Catholic, nativist American Party, better known as the " Know-Nothings", during the early morning hours of March 6, 1854 (a priest replaced it in 1982 using the Latin phrase "A Roma Americae" instead of the original stone's English phrase "Rome to America"). Economic and political conditions of the time caused public contributions to the Washington National Monument Society to cease, so they appealed to Congress for money.: 16, 215, 222-3

The request had just reached the floor of the House of Representatives when the Know-Nothing Party seized control of the Society on February 22, 1855, a year after construction funds ran out. Congress immediately tabled its expected contribution of $200,000 to the Society, effectively halting the Federal appropriation. During its tenure, the Know-Nothing Society added only two courses of masonry, or 4 feet (1.2 m), to the monument using rejected masonry it found on site, increasing the height of the shaft to 156 feet (48 m). The original Society refused to recognize the takeover, so the two rival Societies existed side by side until 1858. With the Know-Nothing Party disintegrating and unable to secure contributions for the monument, it surrendered its possession of the monument to the original Society three and a half years later on October 20, 1858. To prevent future takeovers, the U.S. Congress incorporated the Society on February 22, 1859 with a stated charter and set of rules and procedures.

Post-Civil War

The American Civil War (1861-1865), halted all work on the monument, but interest grew after the war's end. Engineers studied the foundation several times to determine if it was strong enough for continued construction after 20 years of effective inactivity. In 1876, the American Centennial of the Declaration of Independence, Congress agreed to appropriate another $200,000 to resume construction.

Before work could begin again, arguments about the most appropriate design resumed. Many people thought a simple obelisk, one without the colonnade, would be too bare. Architect Mills was reputed to have said omitting the colonnade would make the monument look like "a stalk of asparagus"; another critic said it offered "little ... to be proud of".

This attitude led people to submit alternative designs. Both the Washington National Monument Society and Congress held discussions about how the monument should be finished. The Society considered five new designs, concluding that the one by William Wetmore Story (1819-1895), seemed "vastly superior in artistic taste and beauty". Congress deliberated over those five as well as Mills's original. While it was deciding, it ordered work on the obelisk to continue. Finally, the members of the society agreed to abandon the colonnade and alter the obelisk so it conformed to classical Egyptian proportions.

Construction resumed in 1879 under the direction of Lieutenant Colonel Thomas Lincoln Casey of the United States Army Corps of Engineers. Casey redesigned the foundation, strengthening it so it could support a structure that ultimately weighed more than 40,000 tons (36,000 tonnes). The first stone atop the unfinished stump was laid on August 7, 1880, in a small ceremony attended by President Rutherford B. Hayes, Casey and a few others. The president placed a small coin on which he had scratched his initials and the date in the bed of wet cement at the 150-foot (46 m) level before the first stone was laid on top of it. Casey found 92 memorial stones ("presented stones") already inlaid into the interior walls of the first phase of construction. Before construction continued he temporarily removed eight stones at the 150-foot (46 m) level so that the walls at that level could be sloped outward, producing thinner second-phase walls. He inserted those stones and most of the remaining memorial stones stored in the lapidarium into the interior walls during 1885-1889. The bottom third of the monument is a slightly lighter shade than the rest of the construction because the marble was obtained from different quarries.

The building of the monument proceeded quickly after Congress had provided sufficient funding. In four years, it was completed, with the 100-ounce (2.83 kg) aluminum apex/lightning-rod being put in place on December 6, 1884. The apex was the largest single piece of aluminum cast at the time, when aluminum commanded a price comparable to silver. Two years later, the Hall-Héroult process made aluminum easier to produce and the price of aluminum plummeted, though it should have provided a lustrous, non-rusting apex. The monument opened to the public on October 9, 1888.

The Monument was dedicated on February 21, 1885. Over 800 people were present on the monument grounds to hear speeches during a frigid day by Ohio Senator John Sherman (1823-1900), the Rev. Henderson Suter, William Wilson Corcoran (of the Washington National Monument Society) read by Dr. James C. Welling because Corcoran was unable to attend, Freemason Myron M. Parker, Col. Thomas Lincoln Casey of the Army Corps of Engineers, and President Chester A. Arthur. President Arthur proclaimed:

I do now .... in behalf of the people, receive this monument .... and declare it dedicated from this time forth to the immortal name and memory of George Washington.

After the speeches Lieutenant-General Philip Sheridan (1831-1888), Civil War Cavalry veteran and then General-in-Chief of the United States Army led a procession, which included the dignitaries and the crowd, past the Executive Mansion, now the White House, then via Pennsylvania Avenue to the east main entrance of the Capitol, where 21st President Chester Arthur (1829-1886, served 1881-1885) received passing troops. Then, in the House of Representatives Chamber at the U.S. Capitol, the president, his Cabinet, diplomats and others listened to Representative John Davis Long (1838-1915), (former Lieutenant Governor and Governor of Massachusetts and future Secretary of the Navy) read a speech written a few months earlier by Robert C. Winthrop (1809-1894), formerly the Speaker of the House of Representatives when the cornerstone was laid 37 years earlier in 1848, but now too ill to personally deliver his speech. A final speech was given by John W. Daniel (1842-1910), of Virginia, a well-regarded lawyer, author and Representative (congressman), and Senator. The festivities concluded that evening with fireworks, both aerial and ground displays.

At completion, it was the tallest building in the world, until the Eiffel Tower was completed four years later in Paris in 1889. It is still the tallest building in Washington, D.C. The Heights of Buildings Act of 1910 restricts new building heights to no more than 20 feet (6.1 m) greater than the width of the adjacent street. This monument is taller than the obelisks around the capitals of Europe and in Egypt and Ethiopia, but ordinary antique obelisks were quarried as a monolithic block of stone, and were therefore seldom taller than approximately 100 feet (30 m).

The Washington Monument attracted enormous crowds before it officially opened. For six months after its dedication, 10,041 people climbed the 900 steps and 47 large landings to the top. After the elevator that had been used to raise building materials was altered to carry passengers, the number of visitors grew rapidly, and an average of 55,000 people per month were going to the top by 1888, only three years after its completion and dedication. The annual visitor count peaked at an average of 1.1 million people between 1979 and 1997. From 2005 to 2010, when restrictions were placed on the number of visitors allowed per day, the Washington Monument had an annual average of 631,000 visitors. As with all historic areas administered by the National Park Service (an agency of the U.S. Department of the Interior), the national memorial was listed on the National Register of Historic Places on October 15, 1966.

In the early 1900s, material started oozing out between the outer stones of the first construction period below the 150-foot (46 m) mark, and was referred to by tourists as "geological tuberculosis". This was caused by the weathering of the cement and rubble filler between the outer and inner walls. As the lower section of the monument was exposed to cold and hot and damp and dry weather conditions, the material dissolved and worked its way through the cracks between the stones of the outer wall, solidifying as it dripped down their outer surface.

For ten hours in December 1982, the Washington Monument and eight tourists were held hostage by a nuclear arms protester, Norman Mayer, claiming to have explosives in a van he drove to the monument's base. United States Park Police shot and killed Mayer. The monument was undamaged in the incident, and it was discovered later that Mayer did not have explosives. After this incident, the surrounding grounds were modified in places to restrict the possible unauthorized approach of motor vehicles.

The monument underwent an extensive restoration project between the years of 1998 and 2001. During this time it was completely covered in scaffolding designed by the American architect Michael Graves (who was also responsible for the interior changes). The project included cleaning, repairing and repointing the monument's exterior and interior stonework. The stone in publicly accessible interior spaces was encased in glass to prevent vandalism, while new windows with narrower frames were installed (to increase the viewing space). New exhibits celebrating the life of George Washington, and the monument's place in history, were also added.

On September 7, 2004, the monument closed for a $15 million renovation, which included numerous security upgrades and redesign of the monument grounds by landscape architect Laurie Olin (b. 1938). The renovations were due partly to security concerns following the September 11, 2001 attacks and the start of the War on Terror. The monument reopened April 1, 2005, while the surrounding grounds remained closed until the landscape was finished later that summer.

On August 23, 2011, the Washington Monument sustained damage during the 5.8 magnitude 2011 Virginia earthquake; over 150 cracks were found in the monument. A National Park Service spokesperson reported that inspectors discovered a crack near the top of the structure, and announced that the monument would be closed indefinitely. A block in the pyramidion also was partially dislodged, and pieces of stone, stone chips, mortar, and paint chips came free of the monument and "littered" the interior stairs and observation deck. The Park Service said it was bringing in two structural engineering firms ( Wiss, Janney, Elstner Associates, Inc. and Tipping Mar Associates) with extensive experience in historic buildings and earthquake-damaged structures to assess the monument.

Officials said an examination of the monument's exterior revealed a "debris field" of mortar and pieces of stone around the base of the monument, and several "substantial" pieces of stone had fallen inside the memorial. A crack in the central stone of the west face of the pyramidion was 1 inch (2.5 cm) wide and 4 feet (1.2 m) long. Park Service inspectors also discovered that the elevator system had been damaged, and was operating only to the 250-foot (76 m) level, but was soon repaired.

On September 27, 2011, Denali National Park ranger Brandon Latham arrived to assist four climbers belonging to a "difficult access" team from Wiss, Janney, Elstner Associates. The reason for the inspection was the park agency's suspicion that there were more cracks on the monument's upper section not visible from the inside. The agency said it filled the cracks that occurred on August 23. After Hurricane Irene hit the area on August 27, water was discovered inside the memorial, leading the Park Service to suspect there was more undiscovered damage. The rappellers used radios to report what they found to engineering experts on the ground. Wiss, Janney, Elstner climber Dave Megerle took three hours to set up the rappelling equipment and set up a barrier around the monument's lightning rod system atop the pyramidion; it was the first time the hatch in the pyramidion had been open since 2000.

The external inspection of the monument was completed on October 5, 2011. In addition to the 4-foot (1.2 m) long west crack, the inspection found several corner cracks and surface spalls (pieces of stone broken loose) at or near the top of the monument, and more loss of joint mortar lower down the monument. The full report was issued in December 2011. Bob Vogel, Superintendent of the National Mall and Memorial Parks, emphasized that the monument was not in danger of collapse. "It's structurally sound and not going anywhere", he told the national media at a press conference on September 26, 2011.

On July 9, 2012, the National Park Service announced that the monument would be closed for repairs until 2014. The National Park Service hired construction management firm Hill International in conjunction with joint-venture partner Louis Berger Group to provide coordination between the designer, Wiss, Janney, and Elstner Associates, the general contractor Perini, and numerous stakeholders. NPS said a portion of the plaza at the base of the monument would be removed and scaffolding constructed around the exterior. In July 2013, lighting was added to the scaffolding. Some stone pieces saved during the 2011 inspection would be refastened to the monument, while "Dutchman patches" would be used in other places. Several of the stone lips that help hold the pyramidion's 2,000-pound (910 kg) exterior slabs in place were also damaged, so engineers installed stainless steel brackets to more securely fasten them to the monument.

The National Park Service reopened the Washington Monument to visitors on May 12, 2014, eight days ahead of schedule. Repairs to the monument cost $15 million, with taxpayers funding $7.5 million of the cost and David Rubenstein funding the other $7.5 million. At the reopening Interior Secretary Sally Jewell, show weatherman Al Roker, and American Idol Season 12 winner Candice Glover were present.

The monument continued to be plagued by problems after the earthquake, including in January 2017 when the lights illuminating it went out. The monument was closed again in September 2016 due to reliability issues with the elevator system. On December 2, 2016, the National Park Service announced that the monument would be closed until 2019 in order to modernize the elevator. The $2-3 million project was to correct the elevator's ongoing mechanical, electrical and computer issues, which had shuttered the monument since August 17. The National Park Service requested funding in its FY 2017 President's Budget Request to construct a permanent screening facility for the Washington Monument. The final months of closure were for mitigation of possibly contaminated underground soil thought to have been introduced in the 1880s. The monument reopened September 19, 2019.

After reopening in September 2019, the Washington Monument was closed on March 14, 2020, with the onslaught of the COVID-19 pandemic. It reopened on October 1, 2020, and remained open through the remainder of that year, except for brief closures.

On January 11, 2021, a few days after the storming of the United States Capitol, the National Park Service announced a two-week closure of the monument until after the presidential inauguration due to "credible threats to visitors and park resources". Following a lack of violence, the closure was extended due to a revival of COVID-19 fears.

The monument then reopened on July 14, 2021, only to close yet again on August 16 for two weeks due to lightning strikes which damaged some electrical systems. This occurred just a week before the 10th anniversary of the August 23, 2011 earthquake and highlighted a decade when the monument was closed more than it was open.

On September 20, 2022, the monument was closed for one evening because a man was defacing the monument with red paint and graffiti, "Have u been fucked by this" with an arrow pointing upward and "gov says tough shit" in red lettering at west facing ground level. He was arrested and charged with vandalism but pleaded not guilty in court.

The cornerstone was laid with great ceremony at the northeast corner of the lowest course or step of the old foundation on July 4, 1848. Robert Mills, the architect of the monument, stated in September 1848, "The foundations are now brought up nearly to the surface of the ground; the second step being nearly completed, which covers up the corner stone." Therefore, the cornerstone was laid below the 1848 ground level. In 1880, the ground level was raised 17 feet (5.2 m) to the base of the shaft by the addition of a 30-foot (9.1 m) wide earthen embankment encircling the reinforced foundation, widened another 30 feet in 1881, and then the knoll was constructed in 1887-88. If the cornerstone was not moved during the strengthening of the foundation in 1879-80, its upper surface would now be 21 feet (6.4 m) below the pavement just outside the northeast corner of the shaft. It would now be sandwiched between the concrete slab under the old foundation and the concrete buttress completely encircling what remains of the old foundation. During the strengthening process, about half by volume of the periphery of the lowest seven of eight courses or steps of the old foundation (gneiss rubble) was removed to provide good footing for the buttress. Although a few diagrams, pictures and descriptions of this process exist, the fate of the cornerstone is not mentioned.: 2-7-2-8, 3-3-3-5, 4-3-4-4, B-11-B-18, figs 2.5-2.7, 3.2-3.6, 3.13, 4.8-4.11

The cornerstone was a 24,500-pound (11,100 kg) marble block 2.5 feet (0.76 m) high and 6.5 feet (2.0 m) square with a large hole for a zinc case filled with memorabilia. The hole was covered by a copper plate inscribed with the date of the Declaration of Independence (July 4, 1776), the date the cornerstone was laid (July 4, 1848), and the names of the managers of the Washington National Monument Society. The memorabilia in the zinc case included items associated with the monument, the city of Washington, the national government, state governments, benevolent societies, and George Washington, plus miscellaneous publications, both governmental and commercial, a coin set, and a Bible, totaling 73 items or collections of items, as well as 71 newspapers containing articles relating to George Washington or the monument.: pp 43-46, 109-166

The ceremony began with a parade of dignitaries in carriages, marching troops, fire companies, and benevolent societies.: 16-17, 45-47  A long oration was delivered by the Speaker of the House of Representatives Robert C. Winthrop. Then, the cornerstone was pronounced sound after a Masonic ceremony using George Washington's Masonic gavel, apron and sash, as well as other Masonic symbols. In attendance were President James K. Polk and other federal, state and local government officials, Elizabeth Schuyler Hamilton, Mrs. Dolley Madison, Mrs. John Quincy Adams, and George Washington Parke Custis, among 15,000 to 20,000 others, including a bald eagle. The ceremony ended with fireworks that evening.

States, cities, foreign countries, benevolent societies, other organizations, and individuals have contributed 194 memorial stones, all inserted into the east and west interior walls above stair landings or levels for easy viewing, except one on the south interior wall between stairs that is difficult to view. The sources disagree on the number of stones for two reasons: whether one or both "height stones" are included, and stones not yet on display at the time of a source's publication cannot be included. The "height stones" refer to two stones that indicate height: during the first phase of construction a stone with an inscription that includes the phrase "from the foundation to this height 100 feet" (30 m) was installed just below the 80-90-foot (24-27 m) stairway and high above the 60-70-foot (18-21 m) stairway; during the second phase of construction a stone with a horizontal line and the phrase "top of statue on Capitol" was installed on the 330-foot (100 m) level.

The Historic Structure Report (HSR, 2004) named 194 "memorial stones" by level, including both height stones.: 4-17-4-20, 5-6, "194" on 4-17  Jacob (2005) described in detail and pictured 193 "commemorative stones", including the 100 foot (30 m) stone but not the Capitol stone. The Historic American Buildings Survey (HABS, 1994) showed the location of 193 "memorial stones", but did not describe or name any. HABS showed both height stones, but did not show one stone not yet installed in 1994.: sheets 22-25, 28-30  Olszewski (1971) named 190 "memorial stones" by level, including the Capitol stone but not the 100-foot stone. Olszewski did not include three stones not yet installed in 1971.: chp 6, app D, "190" in chp 6

Of 194 stones, 94 are marble, 40 are granite, 29 are limestone, 8 are sandstone, with 23 miscellaneous types, including stones with two types of material and those whose materials are not identified. Unusual materials include native copper ( Michigan), pipestone ( Minnesota), petrified wood ( Arizona), and jadeite ( Alaska). The stones vary in size from about 1.5 feet (0.46 m) square ( Carthage) to about 6 by 8 feet (1.8 m × 2.4 m) ( Philadelphia and New York City).: 3, 90, 124, 218

Utah contributed one stone as a territory and another as a state, both with inscriptions that include its pre-territorial name, Deseret, both located on the 220-foot (67 m) level.

A stone at the 240-foot (73 m) level of the monument is inscribed in Welsh: Fy Iaith, Fy Ngwlad, Fy Nghenedl, Cymry am byth (My Language, My Country, My Nation, Welsh forever). The stone, imported from Wales, was donated by Welsh citizens of New York. Two other stones were presented by the Sunday Schools of the Methodist Episcopal Church in New York and the Sabbath School children of the Methodist Episcopal Church in Philadelphia -the former quotes from the Bible verse Proverbs 10:7, "The memory of the just is blessed".

Ottoman Sultan Abdul Mejid I donated $30,000 toward the construction of the Washington monument. The Sultans' donation was the largest single donation toward the building of the Washington Monument. The Sultan's intention was to bridge peace between the Ottomans and the Americans. The stone containing the Turkish inscriptions commemorating this event is on the 190-foot (58 m) level. The translation of the inscriptions state, "To support the continuation of true friendship Abdul Mejid Khan's clear and pure name was written on the lofty stone in Washington." It combines the works of two eminent calligraphers: an imperial by Mustafa Rakım's student Haşim Efendi, and an inscription in jalī ta'līq script by Kazasker Mustafa Izzet Efendi, the calligrapher who wrote the giant medallions at Hagia Sophia in Istanbul.

One stone was donated by the Ryukyu Kingdom and brought back by Commodore Matthew C. Perry, but never arrived in Washington (it was replaced in 1989). Many of the stones donated for the monument carried inscriptions that did not commemorate George Washington. For example, one from the Templars of Honor and Temperance stated "We will not make, buy, sell, or use as a beverage, any spiritous or malt liquors, Wine, Cider, or any other Alcoholic Liquor." (George Washington himself had owned a whiskey distillery which operated at Mount Vernon after he left the presidency.)

The aluminum apex, composed of a metal that at the time was as rare and valuable as silver, was cast by William Frishmuth of Philadelphia. At the time of casting, it was the largest piece of aluminum in the world. Before the installation, it was put on public display at Tiffany's in New York City and stepped over by visitors who could say they had "stepped over the top of the Washington Monument". It was 8.9 inches (23 cm) tall before inch (1 cm) was vaporized from its tip by lightning strikes during 1885-1934, when it was protected from further damage by tall lightning rods surrounding it. Its base is 5.6 inches (14 cm) square. The angle between opposite sides at its tip is 34°48'. It weighed 100 ounces (2.83 kg) before lightning strikes removed a small amount of aluminum from its tip and sides. Spectral analysis in 1934 showed that it was composed of 97.87% aluminum with the rest impurities. It has a shallow depression in its base to match a slightly raised area atop the small upper surface of the marble capstone, which aligns the sides of the apex with those of the capstone, and the downward protruding lip around that area prevents water from entering the joint. It has a large hole in the center of its base to receive a threaded 1.5-inch (3.8 cm) diameter copper rod which attaches it to the monument and used to form part of the lightning protection system. In 2015 the National Geodetic Survey reported the coordinates of the 1 mm dimple atop the aluminum apex as (WGS 84).

The four faces of the external aluminum apex all bear inscriptions in cursive writing (Snell Round hand), which are incised into the aluminum. The apex was inscribed on site after it was delivered. Most inscriptions are the original 1884 inscriptions, except for the top three lines on the east face which were added in 1934. From 1885 to 1934 a wide gold-plated copper band that held eight short lightning rods, two per side but not at its corners, covered most of the inscriptions, which were damaged and illegible as shown in the accompanying picture made in 1934. A new band including eight long lightning rods, one at each corner and one at the middle of each side, was added in 1934 and removed and discarded in 2013. The inscriptions that it covered were still damaged and illegible in 2013. Only the top four and bottom two lines of the north face, the first and last lines of the west face, the top four lines of the south face, and the top three lines of the east face are still legible. Even though the inscriptions are no longer covered, no attempt was made to repair them when the apex was accessible in 2013.

The following table shows legible inscriptions in blue and illegible inscriptions in red. No colors appear on the actual apex. The inscriptions occupy the lower portions of triangles, thus the inscribed upper lines are necessarily shorter than some lower lines.

Although most printed sources, Harvey (1903), Olszewski (1971), Torres (1984), and the Historic Structure Report (2004), refer to the original 1884 inscriptions, the National Geodetic Survey (2015) refers to both the 1884 and 1934 inscriptions. All sources print them according to their own editorial rules, resulting in excessive capitalization (Harvey, Olszewski, and NGS) and inappropriate line breaks. No printed source uses cursive writing, although pictures of the apex clearly show that it was used for both the 1884 and 1934 inscriptions.

A replica displayed on the 490-foot level uses totally different line breaks than those on the external apex-it also omits the 1934 inscriptions. In October 2007, it was discovered that the display of this replica was positioned so that the Laus Deo (Latin for "praise be to God") inscription could not be seen and Laus Deo was omitted from the placard describing the apex. The National Park Service rectified the omission by creating a new display.

The pyramidion, the pointed top 55 feet (17 m) of the monument, was originally designed with an 8.9-inch (23 cm) tall inscribed aluminum apex which served as a single lightning rod, installed December 6, 1884. Six months later on June 5, 1885 lightning damaged the marble blocks of the pyramidion, so a net of gold-plated copper rods supporting 200 3-inch (7.6 cm) gold-plated, platinum-tipped copper points spaced every 5 feet (1.5 m) was installed over the entire pyramidion.: 3-10-3-11, 3-15, figs 3.17, 3.23  The original net included a gold-plated copper band attached to the aluminum apex by four large set screws which supported eight closely spaced vertical points that did not protrude above the apex. In 1934 these eight short points were lengthened to extend them above the apex by 6 inches (15 cm). In 2013 this original system was removed and discarded. It was replaced by only two thick solid aluminum lightning rods protruding above the tip of the apex by about one foot (0.3 m) attached to the east and west sides of the marble capstone just below the apex.

Until it was removed, the original lightning protection system was connected to the tops of the four iron columns supporting the elevator with large copper rods. Even though the aluminum apex is still connected to the columns with large copper rods, it is no longer part of the lightning protection system because it is now disconnected from the present lightning rods which shield it. The two lightning rods present since 2013 are connected to the iron columns with two large braided aluminum cables leading down the surface of the pyramidion near its southeast and northwest corners. They enter the pyramidion at its base, where they are tied together (electrically shorted) via large braided aluminum cables encircling the pyramidion two feet (0.6 m) above its base. The bottom of the iron columns are connected to ground water below the monument via four large copper rods that pass through a 2-foot (0.6 m) square well half filled with sand in the center of the foundation. The effectiveness of the lightning protection system has not been affected by a significant draw down of the water table since 1884 because the soil's water content remains roughly 20% both above and below the height of the water table.

During the first phase of construction (1848-1854), the walls were built with bluestone gneiss rubble, ranging from very large irregular stones having a cross section of about 5 by 10 feet (1.5 m × 3.0 m) down to spalls (broken pieces of stone) all embedded in a large amount of mortar. The outer surface is marble stones 14 to 18 inches (36-46 cm) thick in 2-foot (61 cm) high courses or rows horizontally encircling the monument. Although each course contains both stretchers (stones parallel to the wall) and headers (stones projecting into the wall), about two to three times as many stretchers as headers were used. Their joints were so thin that some stones pressed on bare stone below them, breaking off many pieces since it was constructed. The batter or slope of the outer surface is 0.247 inches per foot (2.06 cm/m, 1°11'). The inner surface has disorderly rows of smaller roughly dressed bluestone gneiss.: sheets 7-30  : 18-19, 23, 105-6  The base of the first phase walls has an outer dimension of 55 feet inches (16.80 m) square and a thickness of 15 feet (4.6 m). The interior well is 25 feet 1 inch (7.65 m) square and has square corners. The weight of the first phase walls up to 150 feet (45.7 m) is 22,373 long tons (25,058 short tons; 22,732 tonnes).

During the second phase (1879-1884), the walls were constructed of smoothly dressed ( ashlar) large marble and granite blocks ( rectangular cuboids) laid down in an orderly manner ( Flemish bond) with thick joints. Two-foot high marble surface stones, using an equal number of stretchers and headers, were backed by granite blocks from the 152-foot level (the first course above the rubble) to the 218-foot level, where marble headers become increasingly visible on the internal surface of the walls up to the 450-foot level, above which only marble stones are used. Between the 150- and 160-foot levels the inner walls rapidly slope outward, increasing the shaft well from 25 feet 1 inch square to 31 feet inches (9.59 m) square with a corresponding decrease in the thickness of the walls and their weight. The second phase walls at the 160-foot level were 8 feet inches (2.63 m) thick, which, combined with the larger shaft well, yields an outer dimension of 48 feet inches (14.85 m) square at that level. The top of the second phase walls are 34 feet inches (10.50 m) square and 1 foot 6 inches (46 cm) thick. The second phase interior walls have rounded corners (2-foot (0.61 m) radii). The weight of the second phase walls (from 150 feet to 500 feet) are 21,260 long tons (23,810 short tons; 21,600 tonnes). The walls of the entire shaft (combined first and second phases) are 500 feet inches (152.530 m) high.

The first phase of the walls was constructed under the direction of William Dougherty. Its white Cockeysville marble exterior came from the Texas quarry now adjacent to and east of north I-83 near the Warren Road exit in Cockeysville, Maryland. The quarry was named for the Texas Station (no longer extant) and 19th-century town on the Northern Central Railway. During the first phase it was operated by Thomas Symington, but is now operated by Martin Marietta Materials and no longer produces building stone. The second phase of construction was under the direction of Lt Col/Col Thomas Lincoln Casey of the United States Army Corps of Engineers, who removed two defective courses added by the Know-Nothings and the last 152-foot course added by Dougherty before Casey began his construction. The next three courses of white marble (152-156 feet (46-48 m)) came from Sheffield, Massachusetts, while all courses above them came from the Beaver Dam quarry just west of the 19th-century town of Cockeysville. The latter quarry is located on Beaver Dam Road near its intersection with McCormick Road. During the second phase the quarry was operated by Hugh Sisson, but is now flooded, is called Beaverdam Pond, and is the home of the Beaver Dam Swimming Club. Both 19th-century towns are now within the city limits of Cockeysville.

The marble capstone of the pyramidion is a truncated pyramid with a cubical keystone projecting from its base and a deep groove surrounding the keystone. The aluminum apex replaces its truncated top. The inside upper edges of the topmost slabs on the four faces of the pyramidion rest on the keystone and in the groove. It has a large vertical hole through which a 1.5-inch (3.8 cm) threaded copper rod passes and screws into the base of the apex, which used to form part of its lightning protection system. The keystone and groove occupy so much of its base that only a small horizontal area near its outer edge remains. The weight of the capstone is transferred to both the inner and outer portions of the shiplap upper edges of the slabs. It weighs 3,300 pounds (1,500 kg), is 5 feet 2 inches (1.57 m) high from its base to its top, and is 3 feet (91 cm) square at its base.

The marble pyramidion has an extremely complex construction to save weight yet remain strong. Its surface slabs or panels are usually only 7 inches (18 cm) thick (with small thick and thin portions) and generally do not support the weight of slabs above them, instead transferring their own weight via 1-foot (30 cm) wide internal marble ribs to the shaft's walls. The slabs are generally 7 feet (2 m) wide and 4 feet 4 inches (1 m) high with a 2-inch (5 cm) vertical overlap (shiplap) to prevent water from entering the horizontal joints. Twelve such courses, the internal ribs, the marble capstone, and the aluminum apex comprise the pyramidion. Its height is 55 feet 0 inches (16.76 m). Its weight is 300 long tons (336 short tons; 305 tonnes). The slope of the walls of the pyramidion is 17°24' from the vertical. There are twelve ribs, three per wall, which spring from the 470-foot (143.3 m) level, all being integrated into the walls up to the 500-foot (152.4 m) level. All are free standing above 500 feet, relying on mortise and tenon joints to attach neighboring stones. The eight corner ribs terminate six courses above the shaft, each corner rib resting on its neighboring corner rib via a miter joint, forming four corner arches. Each such arch supports a pair of square corner stones, one above the other totaling one course in height. Each corner rib is linked to the nearest center rib at the sixth course via a marble tie beam. The four center ribs terminate eight courses above the shaft at a marble cruciform (cross shaped) keystone, forming two main arches that cross each other. Two stones, each one course high, are mounted on each of the four ribs, supporting two additional courses above the cruciform keystone, leaving two courses to support the capstone's weight by themselves.

The observation floor (nominally the 500-foot level) is 499 feet inches (152.21 m) above the entry lobby floor or lowest landing level. It is inches (3.2 cm) above the marble base of the pyramidion and the top of the shaft walls.: sheet 7, 31-35

Four pairs of 3-foot (91 cm) wide observation windows are provided, spaced 4 feet (122 cm) apart, inner stone edge to edge, all just above the lowest course of slabs (504-foot level). Six are 1 foot 6 inches (46 cm) high while two on the east face are 2 feet (61 cm) high for easier egress. All were originally provided with thin marble shutters in a bronze frame each of which could be opened inward, one left and the other right per wall. After two people committed suicide by jumping through the open windows in the 1920s, hinged horizontal iron bars were added to them in 1929. A ninth opening in a slab on the south face just below the capstone is provided for access to the outside of the pyramidion. It is covered by a stone slab which is internally removable. In 1931, four red aircraft warning lights were installed, one per face in one of its observation windows. Pilots complained that they could not be easily seen, so the monument was floodlit on all sides as well.: 2-14, B-39, B-41, B-52-B-53  In 1958, eight 14-inch (36 cm) diameter holes for new red aircraft warning lights were bored, one above each window near the top edge of the fourth course of slabs (516-foot level) in the pyramidion.: 2-28, 3-15, B-55  In 1958 the observation windows were glazed with shatterproof glass. In 1974-1976, they were glazed with bulletproof glass and the shutters removed. New bulletproof glass was installed during 1997-2000.: 3-16, 3-18, B-49

The pyramidion has two inscriptions, neither of which is regarded as a memorial stone. One is the year "1884" on the underside of the cruciform keystone; the other is at the same level as that keystone on the north face of the west center rib containing the names and titles of the four highest ranked builders. Its inscription ("Chief Engineer ...") is almost identical to the inscription on the south face of the aluminum apex except for "U.S.", which is part of the phrase "14th U.S. Infantry" in the inscription inside the pyramidion, but the apex has only "14th Infantry". Additionally, the internal inscription does not use cursive writing and all letters in all names are capitals.

The first phase began with the excavation of about 7 feet 8 inches (2.3 m) of topsoil down to a level of loam, consisting of equal parts of sand and clay, hard enough to require picks to break it up. On this "bed of the foundation" the cornerstone was laid at the northeast corner of the proposed foundation. The rest of the foundation was then constructed of bluestone gneiss rubble and spalls, with every crevice filled with lime mortar. The dimensions of this old foundation were 23 feet 4 inches (7.1 m) high, 80 feet (24.4 m) square at the base, and 58 feet 6 inches (17.8 m) square at the top, laid down in eight steps, similar to a truncated step pyramid.: 18-19, 23, 47  At the center of the foundation a brick-lined 2-foot (60 cm) square well was dug to a depth of 20 feet (6 m) below the bed of the foundation to keep it dry and to supply water during construction.

During the second phase, after determining that the proposed weight of the monument was too great for the old foundation to safely bear, the thickness of the walls atop the unfinished stump was reduced and the foundation was strengthened by adding a large unreinforced concrete slab below the perimeter of the old foundation to increase the monument's load bearing area two and one half times. The slab was 13 feet 6 inches (4.1 m) thick, with an outer perimeter 126 feet inches (38.54 m) square, an inner perimeter 44 feet (13.4 m) square, with undisturbed loam inside the inner perimeter except for the water well. The area at the base of the second phase foundation is 15,992 square feet (1,485.7 m ²). The strengthened foundation (old foundation and concrete slab) has a total depth of 36 feet 10 inches (11.2 m) below the bottom of the lowest course of marble blocks (now below ground), and 38 feet (11.6 m) below the entry lobby floor. Casey reported that nowhere did the load exceed 9 long tons per square foot (140 psi; 970 kPa) and did not exceed 3 long tons per square foot (47 psi; 320 kPa) near the outer perimeter. To properly distribute the load from the shaft to slab, about half by volume of the outer periphery of the old rubble foundation below its top step was removed. A continuous sloping unreinforced concrete buttress encircles what remains. The buttress is 100 feet 4 inches (30.6 m) square at its base, 64 feet 6 inches (19.7 m) square at its top, and 20 feet 5 inches (6.2 m) high. The perimeter of the original top step of the old rubble foundation rests on the larger top of the concrete buttress. Its slope (lower external angle from the vertical) is 49°. This buttress rests in a depression (triangular cross-section) on the top surface of the concrete slab. The slab was constructed by digging pairs of 4-foot (1.2 m) wide drifts on opposite sides of the monument's center line to keep the monument properly balanced. The drifts were filled with unreinforced concrete with depressions or dowel stones on their sides to interlock the sections.: 3-3-3-5, figs 3.1-3.6, 3.9, 3.13, 4.11  : 39, 47-48, 67-73  An earthen terrace 60 feet (18 m) wide with its top at the base of the walls and steep sides was constructed in 1880-81 over the reinforced foundation while the rest of the monument was being constructed. During 1887-88, a knoll was constructed around the terrace tapering out roughly 300 feet (90 m) onto the surrounding terrain. This earthen terrace and knoll serves as an additional buttress for the foundation. The weight of the foundation is 36,912 long tons (41,341 short tons; 37,504 tonnes), including earth and gneiss rubble above the concrete foundation that is within its outer perimeter.

The monument is filled with ironwork, consisting of its stairs, elevator columns and associated tie beams, none of which supports the weight of the stonework. It was redesigned in 1958 to reduce congestion and improve the flow of visitors. Originally, visitors entered and exited the west side of the elevator on the observation floor, causing congestion. So the large landing at the 490-foot level was expanded to a full floor and the original spiral stair in the northeast corner between the 490-and-500-foot (149.4 and 152.4 m) levels was replaced by two spiral stairs in the northeast and southeast corners. Now visitors exit the elevator on the observation floor, then walk down either spiral stair before reboarding the elevator for their trip back down.

The main stairs spiral up the interior walls from the entry lobby floor to the elevator reboarding floor at the 490-foot (150 m) level. The elevator occupies the center of the shaft well from the entry lobby to the observation floor, with an elevator machine room (installed 1925-26) whose floor is 18 feet 10 inches (5.74 m) above the observation floor and an elevator pit (excavated 1879) whose floor is 9 feet (2.74 m) below the entry lobby floor.: sheet 31-35  The stairs and elevator are supported by four wrought iron columns each. The four supporting the stairs extend from the entry lobby floor to the observation floor and were set at the corners of a 15-foot-8-inch (4.78 m) square. The four supporting the elevator extend from the floor of the elevator pit to 14 feet (4.3 m) above the observation floor and were set at the corners of a 9-foot--inch (3.0 m) square. The weight of the ironwork is 275 long tons (308 short tons; 279 tonnes). Cast iron, wrought iron, and steel were all used. The two small spiral stairs installed in 1958 are aluminum.

Most landings occupy the entire east and west interior walls every 10 feet (3.05 m) from and including the east landing at the 30-foot (9.1 m) level up to the west landing at the 480-foot (150 m) level, east then west alternately. Three stairs with small landings rise from the entry lobby floor to the 30-foot (9.1 m) level successively along the north, west and south interior walls. Landings from the 30 foot (9.1 m) level up to the 150 foot (46 m) level are 3 feet inches (0.97 m) by 25 feet 1 inch (7.65 m), while landings from the 160-foot (49 m) level to the 480-foot (150 m) level are 7 feet inches (2.41 m) by 31 feet inches (9.59 m). All stairs are on the north and south walls except for the aforementioned west stair between the 10-20-foot (3.05-6.10 m) levels, and the two spiral stairs.[citation needed ]

About one fourth of visitors chose to ascend the monument using the stairs when they were available. They were closed to up traffic in 1971, and then closed to all traffic except by special arrangement in 1976. The stairs had 898 steps until 1958, consisting of 18 risers in each of the 49 main stairs plus 16 risers in the spiral stair. Since 1958 the stairs have had 897 risers if only one spiral stair is counted because both spiral stairs now have 15 risers each.: sheets 6, 31-35  These figures do not include two additional steps in the entry passage that were covered up in 1975 by a ramp and its inward horizontal extension to meet the higher (since 1886) entry lobby floor. One step was 3.2 feet (1 m) away from the outer walls and the other was at the end of the passage, 15 feet (4.6 m) away from the outer walls.: 3-17-3-18, figs 3.11, 3.32-3.33, 3.39

As initially constructed, the interior was relatively open with two-rail handrails, but a couple of suicides and an accidental fall prompted the addition of tall wire screening 7 feet (2.1 m) high with a large diamond mesh) on the inside edge of the stairs and landings in 1929. The original steam powered elevator, which took 10 to 12 minutes to ascend to the observation floor, was replaced by an electric elevator powered by an on-site dynamo in 1901 which took five minutes to ascend. The monument was connected to the electrical grid in 1923, allowing the installation of a modern electric elevator in 1925-26 which took 70 seconds. The latter was replaced in 1958 and again in 1998 by 70-second elevators.: 2-13, 2-15, 3-20-3-21, B-44, B-47, B-48  From 1997 to 2000, the wire screening at three platforms was replaced by large glass panels to allow visitors on the elevator to view three clusters of memorial stones that were synchronously lit as the elevator automatically slowed while passing them during its descent.

Fifty American flags (not state flags), one for each state, are now flown 24 hours a day around a large circle centered on the monument. Forty eight American flags (one for each state then in existence) were flown on wooden flag poles on Washington's birthday since 1920 and later on Independence Day, Memorial Day, and other special occasions until early 1958. Both the flags and flag poles were removed and stored between these days. In 1958 fifty 25-foot (7.6 m) tall aluminum flag poles (anticipating Alaska and Hawaii) were installed, evenly spaced around a 260-foot (79 m) diameter circle. During 2004-05, the diameter of the circle was reduced to 240 feet (73 m). Since Washington's birthday 1958, 48 American flags were flown on a daily basis, increasing to 49 flags on July 4, 1959, and then to 50 flags since July 4, 1960. When 48 and 49 flags were flown, only 48 and 49 flag poles of the available 50 were placed into base receptacles. All flags were removed and stored overnight. Since July 4, 1971, 50 American flags have flown 24 hours a day.: 2-14-2-15, 4-1-4-2, B-35-B-36

In the 2004 grounds renovation, two large circles were added to the landscaping with the obelisk in the intersection or vesica piscis. The monument's vesica piscis is not ideal because neither circle passes through the center of its neighbor. Furthermore, both "circles" are slightly elliptical.

The monument stands 554 feet inches (169.046 m) tall according to the National Geodetic Survey (measured 2013-14) or 555 feet inches (169.294 m) tall according to the National Park Service (measured 1884). In 1975, a ramp covered two steps at the entrance to the monument, so the ground next to the ramp was raised to match its height, reducing the remaining height to the monument's apex. It is both the world's tallest predominantly stone structure and the world's tallest obelisk. It is the tallest monumental column in the world if all are measured above their pedestrian entrances, but two are taller when measured above ground, though they are neither all stone nor true obelisks. The tallest masonry structure in the world is the brick Anaconda Smelter Stack in Montana at 585 feet inches (178.35 m) tall. But this includes a 30-foot (9.1 m) non-masonry concrete foundation, leaving the stack's brick chimney at 555 feet inches (169.20 m) tall, only about 6 inches (15 cm) taller than the monument's 2015 height. If the monument's aluminum apex is also discounted, then the stack's masonry portion is 15 inches (38 cm) taller than the monument's masonry portion.

In 2001, a temporary visitor security screening center was added to the east entrance of the Washington Monument in the wake of the September 11 attacks. The one-story facility was designed to reduce the ability of a terrorist attack on the interior of the monument, or an attempt to seize and hold it. Visitors obtained their timed-entry tickets from the Monument Lodge east of the memorial, and passed through metal detectors and bomb-sniffing sensors prior to entering the monument. After exiting the monument, they passed through a turnstile to prevent them from re-entering. This facility, a one-story cube of wood around a metal frame, was intended to be temporary until a new screening facility could be designed.

On March 6, 2014, the National Capital Planning Commission approved a new visitor screening facility to replace the temporary one. The 785-square-foot (72.9 m ²) facility will be two stories high and contain space for screening 20 to 25 visitors at a time. The exterior walls (which will be slightly frosted to prevent viewing of the security screening process) will consist of an outer sheet of bulletproof glass or polycarbonate, a metal mesh insert, and another sheet of bulletproof glass. The inner sheet will consist of two sheets (slightly separated) of laminated glass. A 0.5-inch (1.3 cm) airspace will exist between the inner and outer glass walls to help insulate the facility. Two (possibly three) geothermal heat pumps will be built on the north side of the monument to provide heating and cooling of the facility. The new facility will also provide an office for National Park Service and United States Park Police staff. The structure is designed so that it may be removed without damaging the monument. The United States Commission of Fine Arts approved the aesthetic design of the screening facility in June 2013.

A recessed trench wall known as a ha-ha has been built to minimize the visual impact of a security barrier surrounding the monument. After the September 11 attacks and another unrelated terror threat at the monument, authorities had put up a circle of temporary Jersey barriers to prevent large motor vehicles from approaching. The unsightly barrier was replaced by a less-obtrusive low 30-inch (76 cm) granite stone wall that doubles as a seating bench and also incorporates lighting. The installation received the 2005 Park/Landscape Award of Merit from the American Society of Landscape Architects.

The Washington Monument is served by Federal Triangle metro station and Smithsonian metro station. Traveling by Metro bus, one can take the DC Circulator on the National Mall route or ride bus number 34, 36, and 32.

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The Washington Monument is an obelisk shaped building within the National Mall in Washington, D.C., built to commemorate George Washington, once commander-in-chief of the Continental Army (1775-1784) in the American Revolutionary War and the first President of the United States (1789-1797).

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My research link and a link to my TinkerCAD. https://www.tinkercad.com/things/hHPbgLjznKo

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The Great Pyramid of Giza is the largest Egyptian pyramid and served as the tomb of pharaoh Khufu, who ruled during the Fourth Dynasty of the Old Kingdom. Built in the early 26th century BC, over a period of about 27 years, the pyramid is the oldest of the Seven Wonders of the Ancient World, and the only wonder that has remained largely intact. It is the most famous monument of the Giza pyramid complex, which is part of the UNESCO World Heritage Site " Memphis and its Necropolis". It is situated at the northern end of the line of the three pyramids at Giza.

The dimensions of the pyramid were 280 royal cubits (146.7 m; 481.4 ft) high, a base length of 440 cubits (230.6 m; 756.4 ft), with a of palms (a slope of 51°50'40").

It was built by quarrying an estimated 2.3 million large blocks, weighing 6 million tonnes in total. The majority of the stones are not uniform in size or shape, and are only roughly dressed. The outside layers were bound together by mortar. Primarily local limestone from the Giza Plateau was used for its construction. Other blocks were imported by boat on the Nile: white limestone from Tura for the casing, and blocks of granite from Aswan, weighing up to 80 tonnes, for the "King's Chamber" structure.

There are three known chambers inside of the Great Pyramid. The lowest was cut into the bedrock, upon which the pyramid was built, but remained unfinished. The so-called Queen's Chamber and King's Chamber, which contain a granite sarcophagus, are above ground, within the pyramid structure. Hemiunu, Khufu's vizier, is believed by some to be the architect of the Great Pyramid. Many varying scientific and alternative hypotheses attempt to explain the exact construction techniques.

The funerary complex around the pyramid consisted of two mortuary temples connected by a causeway (one close to the pyramid and one near the Nile); tombs for the immediate family and court of Khufu, including three smaller pyramids for Khufu's wives; an even smaller "satellite pyramid"; and five buried solar barges.

Pyramid of Menkaure (left), Pyramid of Khafre (center), Great Pyramid (right)

Attribution to Khufu

Historically the Great Pyramid had been attributed to Khufu based on the words of authors of classical antiquity, first and foremost Herodotus and Diodorus Siculus. However, during the Middle Ages other people were credited with the construction of the pyramid as well, for example Joseph from the Book of Genesis, Nimrod, or the legendary king Saurid ibn Salhouk.

In 1837 four additional Relieving Chambers were found above the King's Chamber after tunneling to them. The chambers, previously inaccessible, were covered in hieroglyphs of red paint. The workers who were building the pyramid had marked the blocks with the names of their gangs, which included the pharaoh's name (e.g.: "The gang, The white crown of Khnum-Khufu is powerful"). The names of Khufu were spelled out on the walls over a dozen times. Another of these graffiti was found by Goyon on an exterior block of the 4th layer of the pyramid. The inscriptions are comparable to those found at other sites of Khufu, such as the alabaster quarry at Hatnub or the harbor at Wadi al-Jarf, and are present in pyramids of other pharaohs as well.

Throughout the 20th century the cemeteries next to the pyramid were excavated. Family members and high officials of Khufu were buried in the East Field south of the causeway, and the West Field. Most notably the wives, children and grandchildren of Khufu, Hemiunu, Ankhaf and (the funerary cache of) Hetepheres I, mother of Khufu. As Hassan puts it: "From the early dynastic times, it was always the custom for the relatives, friends and courtiers to be buried in the vicinity of the king they had served during life. This was quite in accordance with the Egyptian idea of the Hereafter."

The cemeteries were actively expanded until the 6th dynasty and used less frequently afterwards. The earliest pharaonic name of seal impressions is that of Khufu, the latest of Pepi II. Worker graffiti was written on some of the stones of the tombs as well; for instance, "Mddw" ( Horus name of Khufu) on the mastaba of Chufunacht, probably a grandson of Khufu.

Some inscriptions in the chapels of the mastabas (like the pyramid, their burial chambers were usually bare of inscriptions) mention Khufu or his pyramid. For instance, an inscription of Mersyankh III states that "Her mother [is the] daughter of the King of Upper and Lower Egypt Khufu." Most often these references are part of a title, for example, Snnw-ka, "Chief of the Settlement and Overseer of the Pyramid City of Akhet-Khufu" or Merib, "Priest of Khufu". Several tomb owners have a king's name as part of their own name (e.g. Chufudjedef, Chufuseneb, Merichufu). The earliest pharaoh alluded to in that manner at Giza is Snefru (Khufu's father).

In 1936 Hassan uncovered a stela of Amenhotep II near the Great Sphinx of Giza, which implies the two larger pyramids were still attributed to Khufu and Khafre in the New Kingdom. It reads: "He yoked the horses in Memphis, when he was still young, and stopped at the Sanctuary of Hor-em-akhet (the Sphinx). He spent a time there in going round it, looking at the beauty of the Sanctuary of Khufu and Khafra the revered."

During excavations in 2013 the Diary of Merer was found at Wadi al-Jarf. It documents the transportation of white limestone blocks from Tura to the Great Pyramid, which is mentioned by its original name Akhet Khufu (with a pyramid determinative) dozens of times. It details that the stones were accepted at She Akhet-Khufu ("the pool of the pyramid Horizon of Khufu") and Ro-She Khufu ("the entrance to the pool of Khufu"), which were under supervision of Ankhhaf, half brother and vizier of Khufu, as well as owner of the largest mastaba of the Giza East Field.

The Great Pyramid has been determined to be about 4600 years old by two principal approaches: indirectly, through its attribution to Khufu and his chronological age, based on archaeological and textual evidence; and directly, via radiocarbon dating of organic material found in the pyramid and included in its mortar.

Historical chronology

In the past the Great Pyramid was dated by its attribution to Khufu alone, putting the construction of the Great Pyramid within his reign. Hence dating the pyramid was a matter of dating Khufu and the 4th dynasty. The relative sequence and synchronicity of events is the focal point of this method.

Absolute calendar dates are derived from an interlocked network of evidence, the backbone of which are the lines of succession known from ancient king lists and other texts. The reign lengths from Khufu to known points in the earlier past are summated, bolstered with genealogical data, astronomical observations, and other sources. As such, the historical chronology of Egypt is primarily a political chronology, thus independent from other types of archaeological evidence like stratigraphies, material culture, or radiocarbon dating.

The majority of recent chronological estimates date Khufu and his pyramid roughly between 2700 and 2500 BC.

Radiocarbon dating

Mortar was used generously in the Great Pyramid's construction. In the mixing process ashes from fires were added to the mortar, organic material that could be extracted and radiocarbon dated. A total of 46 samples of the mortar were taken in 1984 and 1995, making sure they were clearly inherent to the original structure and could not have been incorporated at a later date. The results were calibrated to 2871-2604 BC. The old wood problem is thought to be mainly responsible for the 100-300 year offset, since the age of the organic material was determined, not when it was last used. A reanalysis of the data gave a completion date for the pyramid between 2620 and 2484 BC, based on the younger samples.

History of dating Khufu and the Great Pyramid

Greaves, in 1646, reported the great difficulty of ascertaining a date for the pyramid's construction based on the lacking and conflicting historic sources. Because of the aforementioned differences in spelling, he did not recognize Khufu on Manetho's king list (as transcribed by Africanus and Eusebius),[full citation needed ] hence he relied on Herodotus' incorrect account. Summating the duration of lines of succession, Greaves concluded the year 1266 BC to be the beginning of Khufu's reign.

Two centuries later, some of the gaps and uncertainties in Manetho's chronology had been cleared by discoveries such as the King Lists of Turin, Abydos, and Karnak. The names of Khufu found within the Great Pyramid's Relieving Chambers in 1837 helped to make clear that Cheops and Souphis are, in fact, one and the same. Thus the Great Pyramid was recognized to have been built in the 4th dynasty. The dating among Egyptologists still varied by multiple centuries (around 4000-2000 BC), depending on methodology, preconceived religious notions (such as the biblical deluge) and which source they thought was more credible.

Estimates significantly narrowed in the 20th century, most being within 250 years of each other, around the middle of the third millennium BC. The newly developed radiocarbon dating method confirmed that the historic chronology was approximately correct. It is, however, still not a fully appreciated method due to larger margins or error, calibration uncertainties and the problem of inbuilt age (time between growth and final usage) in plant material, including wood. Furthermore, astronomical alignments have been suggested to coincide with the time of construction.

Egyptian chronology continues to be refined and data from multiple disciplines have started to be factored in, such as luminescence dating, radiocarbon dating, and dendrochronology. For instance, Ramsey et al. included over 200 radiocarbon samples in their model.

Historiographical record

Classical antiquity

The ancient Greek historian Herodotus, writing in the 5th century BC, is one of the first major authors to mention the pyramid. In the second book of his work The Histories, he discusses the history of Egypt and the Great Pyramid. This report was created more than 2000 years after the structure was built, meaning that Herodotus obtained his knowledge mainly from a variety of indirect sources, including officials and priests of low rank, local Egyptians, Greek immigrants, and Herodotus's own interpreters. Accordingly, his explanations present themselves as a mixture of comprehensible descriptions, personal descriptions, erroneous reports, and fantastical legends; as a result, many of the speculative errors and confusions about the monument can be traced back to Herodotus and his work.

Herodotus writes that the Great Pyramid was built by Khufu (Hellenized as Cheops) who, he erroneously relays, ruled after the Ramesside Period (the 19th dynasty and the 20th dynasty). Khufu was a tyrannical king, Herodotus claims, which may explain the Greek's view that such buildings can only come about through cruel exploitation of the people. Herodotus states that gangs of 100,000 labourers worked on the building in three-month shifts, taking 20 years to build. In the first ten years a wide causeway was erected, which, according to Herodotus, was almost as impressive as the construction of the pyramids themselves. It measured nearly 1 kilometre (0.62 mi) long and 20 yards (18.3 m) wide, and elevated to a height of 16 yards (14.6 m), consisting of stone polished and carved with figures.

Underground chambers were made on the hill whereon the pyramids stand. These were intended to be burial places for Khufu himself and were encompassed with water by a channel brought in from the Nile. Herodotus later states that at the Pyramid of Khafre (located beside the Great Pyramid) the Nile flows through a built passage to an island in which Khufu is buried. Hawass interprets this to be a reference to the " Osiris Shaft", which is located at the causeway of Khafre, south of the Great Pyramid.

Herodotus described an inscription on the outside of the pyramid, which, according to his translators, indicated the amount of radishes, garlic and onions that the workers would have eaten while working on the pyramid. This could be a note of restoration work that Khaemweset, son of Rameses II, had carried out. Apparently, Herodotus' companions and interpreters could not read the hieroglyphs or deliberately gave him false information.

Diodorus Siculus

Between 60 and 56 BC, the ancient Greek historian Diodorus Siculus visited Egypt and later dedicated the first book of his Bibliotheca historica to the land, its history, and its monuments, including the Great Pyramid. Diodorus's work was inspired by historians of the past, but he also distanced himself from Herodotus, who Diodorus claims tells marvelous tales and myths. Diodorus presumably drew his knowledge from the lost work of Hecataeus of Abdera, and like Herodotus, he also places the builder of the pyramid, "Chemmis", after Ramses III. According to his report, neither Chemmis ( Khufu) nor Cephren ( Khafre) were buried in their pyramids, but rather in secret places, for fear that the people ostensibly forced to build the structures would seek out the bodies for revenge. With this assertion, Diodorus strengthened the connection between pyramid building and slavery.

The Greek geographer, philosopher, and historian Strabo visited Egypt around 25 BC, shortly after Egypt was annexed by the Romans. In his work Geographica, he argues that the pyramids were the burial place of kings, but he does not mention which king was buried in the structure. Strabo also mentions: "At a moderate height in one of the sides is a stone, which may be taken out; when that is removed, there is an oblique passage to the tomb." This statement has generated much speculation, as it suggests that the pyramid could be entered at this time.

Pliny the Elder

During the Roman Empire, Pliny the Elder argues that "bridges" were used to transport stones to the top of the Great Pyramid.

In pondering how the stones could be transported to such a vast height he gives two explanations: That either vast mounds of nitre and salt were heaped up against the pyramid, which were then melted away with water redirected from the river. Or, that "bridges" were constructed, their bricks afterwards distributed for erecting houses of private individuals, arguing that the level of the river is too low for canals to ever bring water up to the pyramid. Pliny also recounts how "in the interior of the largest Pyramid there is a well, eighty-six cubits [45.1 m; 147.8 ft] deep, which communicates with the river, it is thought". Further, he describes a method discovered by Thales of Miletus for ascertaining the pyramid's height by measuring its shadow.

Late antiquity and the Middle Ages

This late 4th century usage is further confirmed in the geographical treatise Cosmographia, written by Julius Honorius around 376 AD, which explains that the Pyramids were called the "granaries of Joseph" ( horrea Ioseph). This reference from Julius is important, as it indicates that the identification was starting to spread out from pilgrim's travelogues. In 530 AD, Stephanos of Byzantium added more to this idea when he wrote in his Ethnica that the word "pyramid" was connected to the Greek word ( pyros), meaning wheat.

The Abbasid Caliph al-Ma'mun (786-833 CE) is said to have tunneled into the side of the Great Pyramid.

In the seventh century AD, the Rashidun Caliphate conquered Egypt, ending several centuries of Romano-Byzantine rule. A few centuries later, in 832 AD, the Abbasid caliph al-Ma'mun (786-833) is said to have tunneled into the side of the structure and discovered the ascending passage and its connecting chambers. Around this time a Coptic legend gained popularity that claimed the antediluvian king Surid Ibn Salhouk had built the Pyramid. One legend in particular relates how, three hundred years prior to the Great Flood, Surid had a terrifying dream of the world's end, and so he ordered the construction of the pyramids so that they might house all the knowledge of Egypt and survive into the present.

The most notable account of this legend was given by al-Masudi (896-956) in his Akbar al-zaman, alongside imaginative tales about the pyramid, such as the story of a man who fell three hours down the pyramid's well and the tale of an expedition that discovered bizarre finds in the structure's inner chambers. Al-zaman also contains a report of al-Ma'mun's entering the pyramid and discovering a vessel containing a thousand coins, which just so happened to account for the cost of opening the pyramid. (Some speculate that this story is true, but that the coins were planted by Al-Ma'mun to appease his workers, who were likely frustrated that they had found no treasure.)

In 987 AD, the Arab bibliographer Ibn al-Nadim relates a fantastical tale in his about a man who journeyed into the main chamber of a pyramid, which Bayard Dodge argues is the Great Pyramid. According to Ibn al-Nadim, the person in question saw a statue of a man holding a tablet and a woman holding a mirror. Supposedly, between the statues was a "stone vessel [with] a gold cover". Inside the vessel was "something like pitch", and when the explorer reached into the vessel "a gold receptacle happened to be inside". The receptacle, when taken from the vessel, was filled with "fresh blood", which quickly dried up. Ibn al-Nadim's work also claims that the bodies of a man and woman were discovered inside the pyramid in the "best possible state of preservation".

The author al-Kaisi, in his work the Tohfat Alalbab, retells the story of al-Ma'mun's entry but with the additional discovery of "an image of a man in green stone", which when opened revealed a body dressed in jewel-encrusted gold armor. Al-Kaisi claims to have seen the case from which the body was taken, and asserts that it was located at the king's palace in Cairo. He also writes that he himself entered into the pyramid and discovered myriad preserved bodies. Another attempt to enter the pyramid in search of treasure is recorded during the vizierate of al-Afdal Shahanshah (1094-1121), but it was abandoned after a member of the party was lost in the passages.

The Arab polymath Abd al-Latif al-Baghdadi (1163-1231) studied the pyramid with great care, and in his Account of Egypt, he praises them as works of engineering genius. In addition to measuring the structure, alongside the other pyramids at Giza, al-Baghdadi also writes that the structures were surely tombs, although he thought the Great Pyramid was used for the burial of Agathodaimon or Hermes. Al-Baghdadi ponders whether the pyramid pre-dated the Great flood as described in Genesis, and even briefly entertained the idea that it was a pre-Adamic construction. A few centuries later, the Islamic historian Al-Maqrizi (1364-1442) compiled lore about the Great Pyramid in his Al-Khitat. In addition to reasserting that Al-Ma'mun breached the structure in 820 AD, Al-Maqrizi's work also discusses the sarcophagus in the coffin chambers, explicitly noting that the pyramid was a grave.

Construction

Preparation of the site

A hillock forms the base on which the pyramid stands. It was cut back into steps and only a strip around the perimeter was leveled, which has been measured to be horizontal and flat to within 21 millimetres (0.8 in). The bedrock reaches a height of almost 6 metres (20 ft) above the pyramid base at the location of the Grotto.

Along the sides of the base platform a series of holes are cut in the bedrock. Lehner hypothesizes that they held wooden posts used for alignment. Edwards, among others, suggested the usage of water for evening the base, although it is unclear how practical and workable such a system would be.

The Great Pyramid consists of an estimated 2.3 million blocks. Approximately 5.5 million tonnes of limestone, 8,000 tonnes of granite, and 500,000 tonnes of mortar were used in the construction.

Most of the blocks were quarried at Giza just south of the pyramid, an area now known as the Central Field. They are a particular type of nummulitic limestone formed of the fossils of thousands of prehistoric shell creatures, whose small disc form can still be seen in some of the pyramid's blocks upon close inspection. Other fossils have been found in the blocks and other structures on the site, including fossilized shark teeth. The white limestone used for the casing was transported by boat across the Nile from the Tura quarries of the Eastern Desert plateau, about 10 km (6.2 mi) south east of the Giza plateau. In 2013, rolls of papyrus called the Diary of Merer were discovered, written by a supervisor of the deliveries of limestone from Tura to Giza in the 27th year of Khufu's reign.

The granite stones in the pyramid were transported from Aswan, more than 900 km (560 mi) south. The largest, weighing 25 to 80 tonnes, form the ceilings of the "King's chamber" and the "relieving chambers" above it. Ancient Egyptians cut stone into rough blocks by hammering grooves into natural stone faces, inserting wooden wedges, then soaking these with water. As the water was absorbed, the wedges expanded, breaking off workable chunks. Once the blocks were cut, they were carried by boat on the Nile River to the pyramid.

Worker graffiti found at Giza suggest haulers were divided into zau (singular za), groups of 40 men, consisting of four sub-units that each had an "Overseer of Ten".

Surveys and design

The first precise measurements of the pyramid were made by Egyptologist Flinders Petrie in 1880-1882, published as The Pyramids and Temples of Gizeh. Many of the casing-stones and inner chamber blocks of the Great Pyramid fit together with high precision, with joints, on average, only 0.5 millimetres (0.020 in) wide. On the contrary, core blocks were only roughly shaped, with rubble inserted between larger gaps. Mortar was used to bind the outer layers together and fill gaps and joints.

The block height and weight tends to get progressively smaller towards the top. Petrie measured the lowest layer to be 148 centimetres (4.86 ft) high, whereas the layers towards the summit barely exceed 50 centimetres (1.6 ft).

The accuracy of the pyramid's perimeter is such that the four sides of the base have an average error of only 58 millimetres (2.3 inches) in length and the finished base was squared to a mean corner error of only 12 seconds of arc.

The completed design dimensions are measured to have originally been 280 royal cubits (146.7 m; 481.4 ft) high by 440 cubits (230.6 m; 756.4 ft) long at each of the four sides of its base. Ancient Egyptians used seked - how much run for one cubit of rise - to describe slopes. For the Great Pyramid a seked of palms was chosen, a ratio of 14 up to 11 in.

Some Egyptologists suggest this slope was chosen because the ratio of perimeter to height (1760/280 cubits) equals 2 π to an accuracy of better than 0.05 percent (corresponding to the well-known approximation of π as 22/7). Verner wrote, "We can conclude that although the ancient Egyptians could not precisely define the value of π, in practice they used it". Petrie concluded: "but these relations of areas and of circular ratio are so systematic that we should grant that they were in the builder's design". Others have argued that the ancient Egyptians had no concept of pi and would not have thought to encode it in their monuments and that the observed pyramid slope may be based on the seked choice alone.

Alignment to the cardinal directions

The solar gnomon method: The shadow of a vertical rod is tracked throughout a day. The shadow line is intersected by a circle drawn around the base of the rod. Connecting the intersecting points produces an east-west line. An experiment using this method resulted in lines being, on average, 2 minutes, 9 seconds off due east-west. Employing a pinhole produced much more accurate results (19 arc seconds off), whereas using an angled block as a shadow definer was less accurate (3′ 47″ off).

The pole star method: The polar star is tracked using a movable sight and fixed plumb line. Halfway between the maximum eastern and western elongations is true north. Thuban, the polar star during the Old Kingdom, was about two degrees removed from the celestial pole at the time.

The simultaneous transit method: The stars Mizar and Kochab appear on a vertical line on the horizon, close to true north around 2500 BC. They slowly and simultaneously shift east over time, which is used to explain the relative misalignment of the pyramids.

Construction theories

Many alternative, often contradictory, theories have been proposed regarding the pyramid's construction techniques. One mystery of the pyramid's construction is its planning. John Romer suggests that they used the same method that had been used for earlier and later constructions, laying out parts of the plan on the ground at a 1-to-1 scale. He writes that "such a working diagram would also serve to generate the architecture of the pyramid with precision unmatched by any other means".

A casing stone in the British Museum[109]

At completion, the Great Pyramid was cased entirely in white limestone. Precisely worked blocks were placed in horizontal layers and carefully fitted together with mortar, their outward faces cut at a slope and smoothed to a high degree. Together they created four uniform surfaces, angled at 51°50'40" (a seked of palms). Unfinished casing blocks of the pyramids of Menkaure and Henutsen at Giza suggest that the front faces were smoothed only after the stones were laid, with chiseled seams marking correct positioning and where the superfluous rock would have to be trimmed off.

The height of the horizontal layers is not uniform but varies considerably. The highest of the 203 remaining courses are towards the bottom, the first layer being the tallest at 1.49 metres (4.9 ft). Towards the top, layers tend to be only slightly over 1 royal cubit (0.5 m; 1.7 ft) in height. An irregular pattern is noticeable when looking at the sizes in sequence, where layer height declines steadily only to rise sharply again.

So-called "backing stones" supported the casing, which were (unlike core blocks), precisely dressed as well and bound to the casing with mortar.[citation needed ] Now, these stones give the structure its visible appearance, following the partial dismantling of the pyramid in the Middle Ages. Amidst earthquakes in northern Egypt, workers (perhaps the descendants of those who served al-Ma'mun) stripped away many of the outer casing stones, which were said to have been carted away by Bahri Sultan An-Nasir Nasir-ad-Din al-Hasan in 1356 for use in nearby Cairo.

Many more casing stones were removed from the site by Muhammad Ali Pasha in the early 19th century to build the upper portion of his Alabaster Mosque in Cairo.[citation needed ] Later explorers reported massive piles of rubble at the base of the pyramids left over from the continuing collapse of the casing stones, which were subsequently cleared away during continuing excavations of the site. Today a few of the casing stones from the lowest course can be seen on each side, with the best preserved on the north below the entrances, excavated by Vyse in 1837.

The mortar was chemically analyzed and contains organic inclusions (mostly charcoal), samples of which were radiocarbon dated to 2871-2604 BC. It has been theorized that the mortar enabled the masons to set the stones exactly by providing a level bed.

Petrie noted in 1880 that the sides of the pyramid, as we see them today, are "very distinctly hollowed" and that "each side has a sort of groove specially down the middle of the face", which he reasoned was a result of increased casing thickness in these areas. A laser scanning survey in 2005 confirmed the existence of the anomalies, which can be, to some degree, attributed to damaged and removed stones. Under certain lighting conditions and with image enhancement the faces can appear to be split, leading to speculation that the pyramid had been intentionally constructed eight-sided.

Pyramidion and missing tip

The pyramid was once topped by a capstone known as a pyramidion. The material from which it was made is subject to much speculation; limestone, granite or basalt are commonly proposed, while in popular culture it is often solid gold, gilded or electrum. All known 4th dynasty pyramidia (of the Red Pyramid, Satellite Pyramid of Khufu (G1-d) and Queen's Pyramid of Menkaure (G3-a)) are of white limestone and were not gilded. Only from the 5th dynasty onward is there evidence of gilded capstones; for instance, a scene on the causeway of Sahure speaks of the "white gold pyramidion of the pyramid Sahure's Soul Shines".

The Great Pyramid's pyramidion was lost in antiquity, as Pliny the Elder and later authors report a platform on its summit. Now, the pyramid is about 8 metres (26 ft) shorter than it was when intact, with about 1,000 tonnes of material missing from the top.

Elevation diagram of the interior structures of the Great Pyramid viewed from the east. The inner and outer lines indicate the pyramid's present and original profiles.

The internal structure consists of three main chambers (the King's, Queen's and Subterranean Chambers), the Grand Gallery and various corridors and shafts.

There are two entrances into the pyramid: the original and a forced passage, which meet at a junction. From there, one passage descends into the Subterranean Chamber, while the other ascends to the Grand Gallery. From the beginning of the gallery three paths can be taken:

a vertical shaft that leads down, past a grotto, to meet the descending passage

a horizontal corridor leading to the Queen's Chamber

and the path up the gallery itself to the King's Chamber that contains the sarcophagus.

Both the King's and Queen's Chamber have a pair of small "air-shafts". Above the King's Chamber are a series of five Relieving Chambers.

Original entrance

The original entrance is located on the north side, 15 royal cubits (7.9 m; 25.8 ft) east of the centerline of the pyramid. Before the removal of the casing in the Middle Ages, the pyramid was entered through a hole in the 19th layer of masonry, approximately 17 metres (56 ft) above the pyramid's base level. The height of that layer - 96 centimetres (3.15 ft) - corresponds to the size of the entrance tunnel that is commonly called the Descending Passage. According to Strabo (64-24 BC) a movable stone could be raised to enter this sloping corridor; however, it is not known if it was a later addition or original.

A row of double chevrons diverts weight away from the entrance. Several of these chevron blocks are now missing, as indicated by the slanted faces on which they once rested.

North Face Corridor

In February 2023 the North Face Corridor was explored with an endoscopic camera, revealing a horizontal tunnel with a length of 9 metres (30 ft) and a transverse section of about 2 by 2 metres (6.6 by 6.6 ft). Its ceiling is formed by large chevrons, like those visible above the original entrance and also similar to Relieving Chambers.

Robbers' Tunnel

Today tourists enter the Great Pyramid via the Robbers' Tunnel, which was long ago cut straight through the masonry of the pyramid. The entrance was forced into the 6th and 7th layer of the casing, about 7 metres (23 ft) above the base. After running more or less straight and horizontal for 27 metres (89 ft) it turns sharply left to encounter the blocking stones in the Ascending Passage. It is possible to enter the Descending Passage from this point but access is usually forbidden.

Due to a number of historical and archaeological discrepancies, many scholars (with Antoine de Sacy perhaps being the first) contend that this story is apocryphal. They argue that it is much more likely that the tunnel had been carved shortly after the pyramid was initially sealed. This tunnel, the scholars continue, was then resealed (likely during the Ramesside Restoration), and it was this plug that al-Ma'mun's ninth-century expedition cleared away. This theory is furthered by the report of patriarch Dionysius I Telmaharoyo, who claimed that before al-Ma'mun's expedition, there already existed a breach in the pyramid's north face that extended into the structure 33 metres (108 ft) before hitting a dead end. This suggests that some sort of robber's tunnel predated al-Ma'mun, and that the caliph simply enlarged it and cleared it of debris.

Descending Passage

From the original entrance, a passage descends through the masonry of the pyramid and then into the bedrock beneath it, ultimately leading to the Subterranean Chamber.

After 28 metres (92 ft), the lower end of the Ascending Passage is reached; a square hole in the ceiling, which is blocked by granite stones and might have originally been concealed. To circumvent these hard stones, a short tunnel was excavated that meets the end of the Robbers' Tunnel. This was expanded over time and fitted with stairs.

Subterranean Chamber

The Subterranean Chamber, or "Pit", is the lowest of the three main chambers and the only one dug into the bedrock beneath the pyramid.

Located about 27 m (89 ft) below base level, it measures roughly 16 cubits (8.4 m; 27.5 ft) north-south by 27 cubits (14.1 m; 46.4 ft) east-west, with an approximate height of 4 m (13 ft). The western half of the room, apart from the ceiling, is unfinished, with trenches left behind by the quarry-men running east to west. A niche was cut into the northern half of the west wall. The only access, through the Descending Passage, lies on the eastern end of the north wall.

In the middle of the eastern half is a large hole called a Pit Shaft or Perring's Shaft. The uppermost part may have ancient origins, about 2 m (6.6 ft) squared in width and 1.5 m (4.9 ft) in depth, diagonally aligned with the chamber. Caviglia and Salt enlarged it to the depth of about 3 m (9.8 ft). In 1837 Vyse directed the shaft to be sunk to a depth of 50 ft (15 m), in hopes of discovering the chamber encompassed by water that Herodotus alluded to. It is slightly narrower in width at about 1.5 m (4.9 ft). No chamber was discovered after Perring and his workers had spent one and a half years penetrating the bedrock to the then water level of the Nile, some 12 m (39 ft) further down.

The rubble produced during this operation was deposited throughout the chamber. Petrie, visiting in 1880, found the shaft to be partially filled with rainwater that had rushed down the Descending Passage. In 1909, when the Edgar brothers' surveying activities were encumbered by the material, they moved the sand and smaller stones back into the shaft, leaving the upper part clear. The deep, modern shaft is sometimes mistaken to be part of the original design.

Ascending Passage

The Ascending Passage connects the Descending Passage to the Grand Gallery. It is 75 cubits (39.3 m; 128.9 ft) long and of the same width and height as the shaft from which it originates, although its angle is slightly lower at 26°6'.

The lower end of the shaft is plugged by three granite stones, which were slid down from the Grand Gallery to seal the tunnel. They are 1.57 m (5.2 ft), 1.67 m (5.5 ft) and 1 m (3.3 ft) long respectively. The uppermost is heavily damaged, hence it is shorter. The end of the Robbers' Tunnel concludes slightly below the stones, so a short tunnel was dug around them to gain access to the Descending Passage, since the surrounding limestone is considerably softer and easier to work.

Most of the joints between the blocks of the walls run perpendicular to the floor, with two exceptions. Firstly, those in the lower third of the corridor are vertical. Secondly, the three girdle stones that are inserted near the middle (about 10 cubits apart) presumably stabilize the tunnel.

Well Shaft and Grotto

The Well Shaft (also known as the Service Shaft or Vertical Shaft) links the lower end of the Grand Gallery to the bottom of the Descending Passage, about 50 metres (160 ft) further down.

It takes a winding and indirect course. The upper half goes through the nucleus masonry of the pyramid. It runs vertical at first for 8 metres (26 ft), then slightly angles southwards for about the same distance, until it hits bedrock approximately 5.7 metres (19 ft) above the pyramid's base level. Another vertical section descends further, which is partially lined with masonry that has been broken through to a cavity known as the Grotto. The lower half of the Well Shaft goes through the bedrock at an angle of about 45° for 26.5 metres (87 ft) before a steeper section, 9.5 metres (31 ft) long, leads to its lowest point. The final section of 2.6 metres (8.5 ft) connects it to the Descending Passage, running almost horizontally. The builders evidently had trouble aligning the lower exit.

The purpose of the shaft is commonly explained as a ventilation shaft for the Subterranean Chamber and as an escape shaft for the workers who slid the blocking stones of the Ascending Passage into place.

The Grotto is a natural limestone cave that was likely filled with sand and gravel before construction, before being hollowed out by looters. A granite block rests in it that likely originated from the portcullis that once sealed the King's Chamber.

Queen's Chamber

The Horizontal Passage links the Grand Gallery to the Queen's Chamber. Five pairs of holes at the start suggest the tunnel was once concealed with slabs that laid flush with the gallery floor. The passage is 2 cubits (1.0 m; 3.4 ft) wide and 1.17 m (3.8 ft) high for most of its length, but near the chamber there is a step in the floor, after which the passage increases to 1.68 m (5.5 ft) high. Half of the west-wall consists of two layers that have atypically continuous vertical joints. Dormion suggests the entrances to magazines laid here and have been filled in.

The Queen's Chamber is exactly halfway between the north and south faces of the pyramid. It measures 10 cubits (5.2 m; 17.2 ft) north-south, 11 cubits (5.8 m; 18.9 ft) east-west, and has a pointed roof that apexes at 12 cubits (6.3 m; 20.6 ft) tall. At the eastern end of the chamber is a niche 9 cubits (4.7 m; 15.5 ft) high. The original depth of the niche was 2 cubits (1.0 m; 3.4 ft), but it has since been deepened by treasure hunters.

Shafts were discovered in the north and south walls of the Queen's Chamber in 1872 by British engineer Waynman Dixon, who believed shafts similar to those in the King's Chamber must also exist. The shafts were not connected to the outer faces of the pyramid or the Queen's Chamber; their purpose is unknown. In one shaft Dixon discovered a ball of diorite, a bronze hook of unknown purpose and a piece of cedar wood. The first two objects are now in the British Museum. The latter was lost until recently when it was found at the University of Aberdeen. It has since been radiocarbon dated to 3341-3094 BC. The northern shaft's angle of ascent fluctuates and at one point turns 45 degrees to avoid the Great Gallery. The southern shaft is perpendicular to the pyramid's slope.

The shafts in the Queen's Chamber were explored in 1993 by the German engineer Rudolf Gantenbrink using a crawler robot he designed, . After a climb of 65 m (213 ft), he discovered that one of the shafts was blocked by a limestone "door" with two eroded copper "handles". The National Geographic Society created a similar robot, which, in September 2002, drilled a small hole in the southern door only to find another stone slab behind it. The northern passage, which was difficult to navigate because of its twists and turns, was also found to be blocked by a slab.

Grand Gallery

The Grand Gallery continues the slope of the Ascending Passage towards the King's Chamber, extending from the 23rd to the 48th course (of stones), a rise of 21 metres (69 ft). It has been praised as a "truly spectacular example of stonemasonry". It is 8.6 metres (28 ft) high and 46.68 metres (153.1 ft) long. The base is 4 cubits (2.1 m; 6.9 ft) wide, but after two courses - at a height of 2.29 metres (7.5 ft) - the blocks of stone in the walls are corbelled inwards by 6-10 centimetres (2.4-3.9 in) on each side.

At the upper end of the Gallery, on the eastern wall, is a hole near the roof that opens into a short tunnel by which access can be gained to the lowest of the Relieving Chambers.

The floor of the Grand Gallery has a shelf or step on either side, 1 cubit (52.4 cm; 20.6 in) wide, leaving a lower ramp 2 cubits (1.0 m; 3.4 ft) wide between them. There are 56 slots on the shelves, with 28 on each side. On each wall, 25 niches have been cut above the slots. The purpose of these slots is not known, but the central gutter in the floor of the Gallery, which is the same width as the Ascending Passage, has led to speculation that the blocking stones were stored in the Grand Gallery and the slots held wooden beams to restrain them from sliding down the passage. Jean-Pierre Houdin theorized that they held a timber frame that was used in combination with a trolley to pull the heavy granite blocks up the pyramid.

At the top of the gallery, there is a step onto a small horizontal platform where a tunnel leads through the Antechamber, once blocked by portcullis stones, into the King's Chamber.

The Big Void

East-West cut view of the Great Pyramid and front view of the North face Chevron area. a Subterranean chamber, b queen's chamber, c grand gallery, d king's chamber, e descending corridor, f ascending corridor, g al-Ma'mun corridor, h north face Chevron area, i ScanPyramids Big Void with horizontal hypothesis (red hatching) and inclined hypothesis (green hatching) as published in November 2017.[166]

In 2017, scientists from the ScanPyramids project discovered a large cavity above the Grand Gallery using muon radiography, which they called the "ScanPyramids Big Void". A research team, under the supervision of Professor Morishima Kunihiro at Nagoya University, used special nuclear emulsion detectors. Its length is at least 30 metres (98 ft) and its cross-section is similar to that of the Grand Gallery. Its existence was confirmed by independent detection with three different technologies: nuclear emulsion films, scintillator hodoscopes, and gas detectors. The purpose of the cavity is unknown and it is not accessible. Zahi Hawass speculates it may have been a gap used in the construction of the Grand Gallery, but the Japanese research team state that the void is completely different from previously identified construction spaces.

To verify and pinpoint the void, a team from Kyushu University, Tohoku University, the University of Tokyo and the Chiba Institute of Technology planned to rescan the structure with a newly developed muon detector in 2020. Their work was delayed by the COVID-19 pandemic.

Antechamber

The last line of defense against intrusion was a small chamber designed to house portcullis blocking stones, called the Antechamber. It is cased almost entirely in granite and is situated between the upper end of the Grand Gallery and the King's Chamber. Three slots for portcullis stones line the east and west wall of the chamber. Each of them is topped with a semi-circular groove for a log, around which ropes could be spanned.

The granite portcullis stones were approximately 1 cubit (52.4 cm; 20.6 in) thick and were lowered into position by the aforementioned ropes, which were tied through a series of four holes at the top of the blocks. A corresponding set of four vertical grooves are on the south wall of the chamber, recesses that make space for the ropes.

The Antechamber has a design flaw: the space above them can be accessed, thus all but the last block can be circumvented. This was exploited by looters who punched a hole through the ceiling of the tunnel behind, gaining access to the King's Chamber. Later on, all three portcullis stones were broken and removed. Fragments of these blocks can be found in various locations in the pyramid (the Pit Shaft, the Original Entrance, the Grotto and the recess before the Subterranean Chamber).

King's Chamber

The walls consist of five courses of blocks that are uninscribed, as was the norm for burial chambers of the 4th dynasty. The stones are precisely fitted together. The facing surfaces are dressed to varying degrees, with some displaying remains of lifting bosses not entirely cut away. The back sides of the blocks were only roughly hewn to shape, as was usual with Egyptian hard-stone facade blocks, presumably to save work.

Sarcophagus

The only object in the King's Chamber is a sarcophagus made of a single, hollowed-out granite block. When it was rediscovered in the Early Middle Ages, it was found broken open and any contents had already been removed. It is of the form common for early Egyptian sarcophagi, rectangular in shape with grooves to slide the now missing lid into place with three small holes for pegs to fixate it. The coffer was not perfectly smoothed, displaying various tool marks matching those of copper saws and tubular hand-drills.

The internal dimensions are roughly 198 cm (6.50 ft) by 68 cm (2.23 feet), the external 228 cm (7.48 ft) by 98 cm (3.22 ft), with a height of 105 cm (3.44 ft). The walls have a thickness of about 15 cm (0.49 ft). The sarcophagus is too large to fit around the corner between the Ascending and Descending Passages, which indicates that it must have been placed in the chamber before the roof was put in place.

In the north and south walls of the King's Chamber are two narrow shafts, commonly known as "air shafts". They face each other and are located approximately 0.91 m (3.0 ft) above the floor, 2.5 m (8.2 ft) from the eastern wall, with a width of 18 and 21 cm (7.1 and 8.3 in) and a height of 14 cm (5.5 in). Both start out horizontally for the length of the granite blocks they go through before changing to an upwards direction.

The southern shaft ascends at an angle of 45° with a slight curve westwards. One ceiling stone was found to be distinctly unfinished, which Gantenbrink called a "Monday morning block". The northern shaft changes angle several times, shifting the path to the west, perhaps to avoid the Big Void. The builders apparently had trouble calculating the right angles, resulting in parts of the shaft being narrower. Now, they both commute to the exterior. Whether they originally penetrated the outer casing is unknown.

The purpose of these shafts is not clear: They were long believed by Egyptologists to be shafts for ventilation, but this idea has now been widely abandoned in favour of the shafts serving a ritualistic purpose associated with the ascension of the king's spirit to the heavens.

In 1992, as part of the Upuaut project, a ventilation system was installed in both air shafts of the King's Chamber.

Relieving chambers

Above the roof of the King's Chamber are five compartments, named (from lowest upwards) " Davison's Chamber", " Wellington's Chamber", " Nelson's Chamber", " Lady Arbuthnot's Chamber", and " Campbell's Chamber".

They were presumably intended to safeguard the King's Chamber from the possibility of the roof collapsing under the weight of stone above; hence they are referred to as "Relieving Chambers".

The granite blocks that divide the chambers have flat bottom sides but roughly shaped top sides, giving all five chambers an irregular floor, but a flat ceiling, with the exception of the uppermost chamber, which has a pointed limestone roof.

Nathaniel Davison is credited with the discovery of the lowest of these chambers in 1763, although a French merchant named Maynard informed him of its existence. It can be reached through an ancient passage that originates from the top of the south wall of the Grand Gallery. The upper four chambers were discovered in 1837 by Howard Vyse after discovering a crack in the ceiling of the first chamber. This allowed the insertion of a long reed, which, with the employment of gunpowder and boring rods, opened a tunnel upwards through the masonry. As no access shafts existed for the upper four chambers - unlike Davison's Chamber - they were completely inaccessible until this point.

Numerous graffiti of red ochre paint were found covering the limestone walls of all four newly discovered chambers. Apart from leveling lines and indication marks for masons, multiple hieroglyphic inscriptions spell out the names of work-gangs. Those names, which were also found in other Egyptian pyramids like that of Menkaure and Sahure, usually included the name of the pharaoh for whom they were working. The blocks must have received the inscriptions before the chambers became inaccessible during construction. Their orientation, often side-ways or upside down, and their sometimes being partially covered by blocks, seems to indicate that the stones were inscribed before being laid.

The inscriptions, correctly deciphered only decades after discovery, read as follows:

"The gang, The Horus Mededuw-is-the-purifier-of-the-two-lands". Found once in relieving chamber 3. (Mededuw being Khufu's Horus name.)

"The gang, The Horus Mededuw-is-pure" Found seven times in chamber 4.

"The gang, Khufu-excites-love" Found once in chamber 5 (top chamber).

"The gang, The-white-crown-of Khnumkhuwfuw-is-powerful" Found once in chambers 2 and 3, ten times in chamber 4 and twice in chamber 5. (Khnum-Khufu being Khufu's full birth name.)

Pyramid complex

The Great Pyramid is surrounded by a complex of several buildings, including small pyramids.

Temples and causeway

East cemetery

Subsidiary pyramids

On the southern end of the east side are four subsidiary pyramids The three that remain standing to almost full height are popularly known as the Queens' Pyramids ( G1-a, G1-b and G1-c). The fourth, smaller satellite pyramid ( G1-d), is so ruined that its existence was not suspected until the first course of stones and, later, the remains of the capstone were discovered during excavations in 1991-1993.

Three boat-shaped pits are located east of the pyramid. They are large enough in size and shape to have held complete boats, though so shallow that any superstructure, if there ever was one, must have been removed or disassembled.

Two additional boat pits, long and rectangular in shape, were found south of the pyramid, still covered with slabs of stone weighing up to 15 tons.

The first of these was discovered in May 1954 by the Egyptian archaeologist Kamal el-Mallakh. Inside were 1,224 pieces of wood, the longest 23 metres (75 ft) in length, the shortest 10 centimetres (0.33 ft). These were entrusted to a boat builder, Haj Ahmed Yusuf, who worked out how the pieces fit together. The entire process, including conservation and straightening of the warped wood, took fourteen years. The result is a cedar-wood boat 43.6 metres (143 ft) long, its timbers held together by ropes, which was originally housed in the Giza Solar boat museum, a special boat-shaped, air-conditioned museum beside the pyramid. The boat is now in the Grand Egyptian Museum.

During construction of this museum in the 1980s, the second sealed boat pit was discovered. It was left unopened until 2011 when excavation began on the boat.

Pyramid town

A notable construction flanking the Giza pyramid complex is a cyclopean stone wall, the Wall of the Crow. Mark Lehner discovered a worker's town outside of the wall, otherwise known as "The Lost City", dated by pottery styles, seal impressions and stratigraphy to have been constructed and occupied sometime during the reigns of Khafre (2520-2494 BC) and Menkaure (2490-2472 BC). In the early 21st century, Lehner and his team made several discoveries, including what appears to have been a thriving port, suggesting the town and associated living quarters, which consisted of barracks called "galleries", may not have been for the pyramid workers after all, but rather for the soldiers and sailors who used the port. In light of this new discovery, as to where then the pyramid workers may have lived, Lehner suggested the alternative possibility they may have camped on the ramps he believes were used to construct the pyramids, or possibly at nearby quarries.

In the early 1970s, the Australian archaeologist Karl Kromer excavated a mound in the South Field of the plateau. It contained artefacts including mudbrick seals of Khufu, which Kromer identified with an artisans' settlement. Mudbrick buildings just south of Khufu's Valley Temple contained mud sealings of Khufu and have been suggested to be a settlement serving the cult of Khufu after his death. A worker's cemetery used at least between Khufu's reign and the end of the Fifth Dynasty was discovered south of the Wall of the Crow by Hawass in 1990.

Authors Bob Brier and Hoyt Hobbs claim that "all the pyramids were robbed" by the New Kingdom, when the construction of royal tombs in the Valley of the Kings began. Joyce Tyldesley states that the Great Pyramid itself "is known to have been opened and emptied by the Middle Kingdom", before the Arab caliph Al-Ma'mun entered the pyramid around 820 AD.

I. E. S. Edwards discusses Strabo's mention that the pyramid "a little way up one side has a stone that may be taken out, which being raised up there is a sloping passage to the foundations". Edwards suggested that the pyramid was entered by robbers after the end of the Old Kingdom and sealed and then reopened more than once until Strabo's door was added. He adds: "If this highly speculative surmise be correct, it is also necessary to assume either that the existence of the door was forgotten or that the entrance was again blocked with facing stones", in order to explain why al-Ma'mun could not find the entrance. Scholars such as Gaston Maspero and Flinders Petrie have noted that evidence for a similar door has been found at the Bent Pyramid of Dashur.

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Further reading

External links

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The Great Pyramid of Giza is the largest Egyptian pyramid and served as the tomb of pharaoh Khufu, who ruled during the Fourth Dynasty of the Old Kingdom. Built in the early 26th century BC, over a period of about 27 years, the pyramid is the oldest of the Seven Wonders of the Ancient World, and the only wonder that has remained largely intact.