Changsha - Sky City (天空城市)

Sky City (Chinese: 天空城市; pinyin: tiānkōng chéngshì), or Sky City One, is a proposed supertall skyscraper approved for construction in the city of Changsha, Hunan in south-central China, to be constructed by the Chinese construction company Broad Sustainable Building.[5]
If built as planned and to schedule, Sky City would be likely to be the tallest building in the world at the time of its completion, with 220 floors and a total height of 838 meters. The construction plan calls for it to be built from pre-fabricated units constructed on site in an unprecedentedly short period of 90 days.[6][7] BSB's plan is to assemble 95% of the building in its factory before a single shovelful of dirt has been moved at the actual build site.[8]
The proposed building will have total floor space of 1.2 million m2. The main building will be 1.05 million m2, a basement of 130,000 m2 and a 3–7 floor high annex of 35,000 m2.[2]
A cost estimate of $1500 per square meter[9] of floor space would make Sky City considerably cheaper than the similarly tall Burj Khalifa ($4500 per square meter).
As of October 2012, BSB has received approval from the government[8] and has stated that they are still going to begin construction in November, but announced a new build time of 210 days. This puts the date of completion at May 2013.[10]
On November 16, Juliet Jiang, senior vice president of Broad Group, said in an interview that the company will adhere to its previous time table of building five floors a day and completing the building in a 90 day time frame. She also said the building is still waiting for government approval.[9]
Later in November, the company announced January 2013 as the start for the construction.[11]
Although structural details are not available, outside architects have expressed doubts that a modular design would have the stiffness on lower floors to withstand the wind loads imposed by such a height, without unacceptable amounts of sway,[12] or that the building could be built without high-strength concrete, whose curing time would preclude such a rapid construction rate.

Source (Wikipedia)