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The projected 1km-high building in Jeddah, Saudi Arabia is set to be the world's tallest, but what's interesting is that it was meant to be a kilometre-and-a-half. So what's stopping us from going higher?

The first major problem is wind: what feels like a gentle breeze at ground level can feel like a howling gale 500m up - as engineer William LeMessurier found out in 1978 when he just completed the 278m Citicorp Center in New York. An undergraduate architecture student asked him whether the building could blow over in the wind, and LeMessurier discovered to his horror that the design had accounted for perpendicular winds, but not winds angled at 45 degrees to the building. Workmen were sent in at night to make the building safe by welding steel plates to the wind braces., and this was kept a secret from the public for nearly 20 years.

These days, ingenious solutions are used to wind-proof skyscrapers, like the Taipei 101 in Taiwan. It's topped off with a giant pendulum that swings in the opposite direction to the wind when a typhoon strikes.

Skyscrapers also need a big base, which limits their space saving potential. Dubai's 828m-tall Burj Khalifa Tower offers a clever solution. A unique Y-shaped design with a hexagonal core and three wings has been used to create perfect stability.

The biggest problem, though? Elevators. Technologically, designers and engineers have hit the ceiling, and we have no solution yet. The issue is that cables longer than 600m are simply too heavy to winch. So, until we can solve this, the dream of the 5km-high megatower will remain a fantasy.

For more from BBC's Factomania . If you would like to comment on this article or anything else you have seen on Future, head over to our Facebook page or message us on .

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The projected 1km-high building in Jeddah, Saudi Arabia is set to be the world's tallest, but what's interesting is that it was meant to be a kilometre-and-a-half. So what's stopping us from going higher?

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Resources for Primary and Secondary Students - ABC Education

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4000+ educational games, videos and teaching resources for schools and students. Free Primary and Secondary resources covering history, science, English, maths and more

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Aldar HQ Abu Dhabi Worlds First Round Skyscraper Documentary National Geographic

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Burj Khalifa Documentary National Geographic

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Mega Structures - Burj Khalifa, Dubai [National Geographic] in English

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Uploaded by Bubla chatterjee on 2014-02-07.

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Sky Scraper Builders:Super tools of the high rise Documentary

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Sky Scraper Builders:Super tools of the high rise - Documentary Subscribe: . These tools are high impact, cutting edge and big, really big. Their challenge: built hundreds of feet straight up. The indispensable tools of the high rise, taking us . The design and construction of skyscrapers involves creating safe, habitable spaces in very tall buildings.

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Timelapse Video of a Skyscraper being built

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Timelapse Video of a Skyscraper being built

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A Chinese development company builds a 57-storey tower in a record 19 days in Changsha, Hunan Province in southern China. The video shows a Mini Sky City skyscraper built at a brick-by-brick rate of three full levels per day. To see more videos from the Broad Group visit its website

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Chinese build 57-storey skyscraper in 19 days - timelapse video

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A Chinese development company builds a 57-storey tower in a record 19 days in Changsha, Hunan Province in southern China. The video shows a Mini Sky City skyscraper built at a brick-by-brick rate of three full levels per day. To see more videos from the Broad Group visit its website

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Skyscrapers - Mega-Bracing for High Winds Video

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Skyscrapers - Mega-Bracing for High Winds Video

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Skyscrapers - Mega-Bracing for High Winds

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Workers work 10-12 hours a day, six days per week, to build a skyscraper on budget and on time. (From Discovery Channel's "Understanding Skyscrapers") Become a fan here! https://www.facebook.com/HowWeInventedTheWorld

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Website about skyscrapers and lots of links

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Wonders of the World Databank How long does it take to wash an 88-story skyscraper? What's the tallest building ever built in a major earthquake zone?

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Hello Kids Today - The Tallest Building! Construction of Kingdom Tower Has Begun

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Daily world news that interest kids -- handpicked and revised articles that kids of the future need to and want to know about. We are currently accepting young participants to join the fun online (via Google Hangout or Skype) every day from Monday to Friday. www.hellokidstoday.com