Firm Plans to Build World's Tallest Building ... in 90 Days Chinese company plans prefab 'Sky City' By Rob Quinn, Newser Staff Posted Nov 26, 2012 1:00 AM CST 20 comments Comments An artist's impression of the proposed 'Sky City.' (Wikipedia) (Newser) – A Chinese company is planning to make the world's tallest building sprout from the central city of Changsha as fast as a magic beanstalk. Broad Sustainable Building says that after construction begins on its Sky City project early next year, the 2,749-foot-tall tower will be completed in just 90 days, the New York Daily News reports. Workers assembling prefabricated blocks of the building will add up to five floors a day, the firm said. The tower, which the company says will house thousands of people as well as a hotel and a hospital, will be at least 10 feet taller than Dubai's Burj Khalifa, which took more than five years to build. Plenty of skeptics doubt the company will be able to finish the 220-story tower on time, though it successfully built a 30-story tower in 15 days last year and put up a 15-story hotel in just 48 hours in 2010.