But even more astonishing is the speed at which this giant is to be raised -- according to engineers, its 220 floors are to grow in a mere 90 days in Changsha, the capital city of China's south-central Hunan Province.
Foundation work is to begin at the end of the month once the Chinese authorities give the final go ahead to the project.
According to the construction company BROAD Sustainable Building (BSB), the skyscraper will be erected at the rate of five floors per day thanks to a prefabricated modular technology.
This method was used in the firm’s construction of a 30-story hotel in 15 days in Hunan Province in December 2011:
Sky City was designed by some of the architects and engineers who previously worked at Dubai’s 830-meter high Burj Khalifa -- today’s tallest building in the world.
But whereas the Burj Khalifa cost $1.5 billion, Sky City is expected to come to just $628 million.
David Scott, the lead structural director with the international engineering enterprise Laing O’Rourke, says that’s thanks to the prefab technology that allows construction companies to build the components in a factory and later have them assembled on site.
"It makes it very fast and you can optimize on your component designs so it makes it cheap," Scott says. "The fact that it's cheaper comes from two particular areas. One is that it's very quick to build, so if you're going to build it in under a year compared to10 years, you don't have that big investment cost that the Burj Khalifa attracted. You're reducing your site labor enormously because it's all been done in a factory, so you don't have down time for weather or for all the other components that happen when you're building things by pumping concrete and lifting reinforcement cages into positions."
With the planned construction, BSB says, the objective is to "promote a high quality of life through lively urban design."
Sky City will be able to house 31,400 people.
Residential space will take up most of the building, which will also house offices, schools, hospitals, shops, and restaurants, with people moving up and down using 104 high-speed elevators.
Some 220,000 tons of steel are to be used for the construction, which BSB claims will be able to sustain earthquakes of a 9.0 magnitude thanks to a "trapezoidal pyramid solid structure."
As for the fireproof steel structure, it is to be resistant "up to three hours."
BSB says it intends to develop a "practical building with medium cost and ultralow energy consumption which will reciprocally shape the future urban lifestyle.”
Its developers say Sky City will be five times more energy efficient than a conventional building, use one-sixth of a typical building's electricity consumption, and have air that is 20 times purer than outdoor air.
Thanks to the prefab technology, BSB estimates it will cost $1,500 per square meter as opposed to the Burj's $15,000 per square meter, technology and design blog Gizmodo reports.
But skepticism has arisen about this project.
Arabianbusiness.com quoted Bart Leclercq, an associate director for engineering firm WSP Middle East, as saying in August: "If you are doing it for half of the cost it suggests you are only putting half of the materials in there, which means you will only have half the stiffness and half the strength. I think this is not going to fly."