A Chinese construction company built a 57-story skyscraper – and it only took 19 days. Broad Sustainable Building said the Mini Sky City building, located in the Hunan provincial capital of Changsha, has 800 apartments and office space for 4,000 workers. The company used a "modular method," piecing together the structure at the rapid pace of three floors per day, they said. The Changsha-based company spent 4½ months fabricating the building's 2,736 modules before construction began. “The first 20 floors were completed last year, and the remaining 37 were built from Jan. 31 to Feb. 17 this year”, Xiao said. “The company has honed its technology to accelerate its construction speed from two floors to three floors a day”, he said. Up next, the company hopes to assemble a 220-floor skyscraper over just three months in Changsha.