Some are worried the building could be vulnerable to safety hazards, due to the unconventional construction technique devised by Broad Group.
That "fast-building technology" allowed the group to put up a 30-story tower in 15 days in 2011, and a 15-story hotel within six days a year earlier.
Zhi Yin, head of Beijing Tsinghua Urban Planning Academy, told Xinhua, China's government-sanctioned media body, that Sky City would be "either a marvel or a hoax."
According to Yin, Broad Group's Sky City is an experiment, he claims, that still needs a practical test.
Yin Lu, an architect from Baojia Group, expressed concerns to Xinhua about subsidence when the building gets higher.
Broad Group emphasized that relevant authorities have approved the building as safe.
Super-fast construction method
The construction technique is simple, according to the company.
Some 20,000 workers in BSB's offsite factory produce thousands of prefabricated steel-and-concrete blocks, 60 square meters in size, over four months.
These blocks are transported to the location, hoisted and packed into position to make up the final structure over two months, at a rate of three stories a day.
Another four months are needed to complete the internal construction.
Broad Group has applied this method to more than 30 of their buildings.
There remains a certain amount of skepticism about the feasibility of the project from Chinese public and experts.
The world should know the truth early next year.