Tenochtitlan covered an estimated 8 to 13.5 km² (3.1 to 5.2 sq mi), situated on the western side of the shallow Lake Texcoco.

At the time of Spanish conquests, Mexico City comprised Tenochtitlan and Tlatelolco at the same time. Since then, the city extended from north to south from the north border of Tlatelolco to the swamps, which by that time were gradually disappearing to the west, the city ended more or less at the present location of Bucareli Street.

It was connected to the mainland by causeways leading north, south, and west of the city. These causeways were interrupted by bridges that allowed canoes and other traffic to pass freely. The bridges could be pulled away if necessary to defend the city. The city was interlaced with a series of canals, so that all sections of the city could be visited either on foot or via canoe.

Lake Texcoco was the largest of the five interconnected lakes. Since it formed in an endorheic basin lake, Lake Texcoco was brackish. During the reign of Montezuma I, the "levee of Nezahualcoyotl" was constructed, reputedly designed by Nezahualcoyotl. Estimated to be 12 to 16 km (7.5 to 9.9 mi) in length, the levee was completed circa 1453; the levee kept the spring-fed fresh water in the waters around Tenochtitlan and kept the brackish waters beyond the dike, to the east.

Two double aqueducts, each more than 4 km (2.5 mi) long and made of terracotta, provided the city with fresh water from the springs at Chapultepec. This was intended mainly for cleaning and washing. For drinking, water from mountain springs was preferred. Most of the population liked to bathe twice a day; Moctezuma was said to take four baths a day. As soap they used the root of a plant called copalxocotl (Saponaria americana); to clean their clothes they used the root of metl (Agave americana). Also, the upper classes and pregnant women enjoyed the temazcalli. Similar to a sauna bath, it is still used in the south of Mexico. This was also popular in other Mesoamerican cultures.

When used about ethnic groups the term "Aztec" refers to several Nahuatl speaking peoples of central Mexico in the postclassic period of Mesoamerican chronology, especially the ethnic group that had a leading role in establishing the hegemonic empire based at Tenochtitlan, the Mexica. Other ethnic groups associated with the Aztec empire are the Acolhua and Tepanec ethnic groups and some of the ethnic groups that were incorporated into the empire, and the term is also sometimes used about them. In older usage the term was commonly used about modern Nahuatl speaking ethnic groups, as Nahuatl was previously referred to as the "Aztec language". In recent usage these ethnic groups are rather referred to as the Nahua peoples. Linguistically the term "Aztecan" is still used about the branch of the Uto-Aztecan languages (also sometimes called the yuto-nahuan languages) that includes the Nahuatl language and its closest relatives Pochutec and Pipil.

To the Aztecs themselves the word "aztec" was not an endonym for any particular ethnic group. Rather it was an umbrella term used to refer to several ethnic groups, not all of them Nahuatl speaking, that claimed heritage from the mythic place of origin, Aztlan. In the Nahuatl language "aztecatl" means "person from Aztlan". In 1810 Alexander von Humboldt originated the modern usage of "Aztec" as a collective term applied to all the people linked by trade, custom, religion, and language to the Mexica state and the Triple Alliance. In 1843, with the publication of the work of William H. Prescott, it was adopted by most of the world, including 19th century Mexican scholars who saw it as a way to distinguish present-day Mexicans from pre-conquest Mexicans. This usage has been the subject of debate in more recent years, but the term "Aztec" is still more common.

Mictlantecuhtli was a god of the dead and the king of Mictlan, the lowest and northernmost section of the underworld. He was one of the principal gods of the Aztecs and was the most prominent of several gods and goddesses of death and the underworld. The worship of Mictlantecuhtli sometimes involved ritual cannibalism, with human flesh being consumed in and around the temple.

The city was built on wooden pilings were driven into the lake bed to create a stable foundation. The stones that were used to build this capital were hauled to the "swamp city" to build the massive structures. From being a tribe of nomades to becoming a distingwished ruling empire, the Aztecs, in my opinion, were the over achevers.

At the time of Spanish conquest, Mexico City comprised Tenochtitlan and Tlatelolo at the same time. Since then, the city extended from north to south from the north border of Tlatelolco to the swamps which by that time were gradually disappearing to the west, the city ended more or less at the present location of Bucareli Street, present day Mexico City.

While human sacrifice was practiced throughout Mesoamerica, the Aztecs, if their own accounts are to be believed, brought this practice to an unprecedented level. For example, for the reconsecration of the Great Pyramid of Tenochtitlan in 1487, the Aztecs reported that they sacrificed 84,400 prisoners over the course of four days, reportedly by Ahuitzotl, the Great Speaker himself. This number, however,is not universally accepted.

Accounts by the Tlaxcaltecas, the primary enemy of the Aztecs at the time of the Spanish Conquest, show that at least some of them considered it an honor to be sacrificed. In one legend, the warrior Tlahuicole was freed by the Aztecs but eventually returned of his own volition to die in ritual sacrifice. Tlaxcala also practiced the human sacrifice of captured Aztec Citizens.

While human sacrifice was practiced throughout Mesoamerica, the Aztecs, if their own accounts are to be believed, brought this practice to an unprecedented level. For example, for the reconsecration of the Great Pyramid of Tenochtitlan in 1487, the Aztecs reported that they sacrificed 84,400 prisoners over the course of four days, reportedly by Ahuitzotl, the Great Speaker himself. This number, however,is not universally accepted.

Accounts by the Tlaxcaltecas, the primary enemy of the Aztecs at the time of the Spanish Conquest, show that at least some of them considered it an honor to be sacrificed. In one legend, the warrior Tlahuicole was freed by the Aztecs but eventually returned of his own volition to die in ritual sacrifice. Tlaxcala also practiced the human sacrifice of captured Aztec Citizens.