A Chinese company has seemingly accomplished the impossible, putting up a 30-story building in half as many days.  Broad Sustainable Building finished construction on the 30-story hotel prototype in the city of Changsha after only 15 days of construction.

The construction was able to proceed so fast because the foundation was laid ahead of time and the building was largely factory manufactured. Once the pieces were shipped to the site all that was left was for the construction workers to put it all together, which they did at record speed.

According to Broad Sustainable Building’s website, the building was 93 percent factory made, a process which they say eliminates the risks associated with design and construction quality, budget and construction delays.

Critics, however, question the safety the building, pointing to the lack of oversight and pace at which it went up.

Broad Sustainable Building has attempted projects like this before, building a 15-story hotel in just a week as well as a six-story pavilion in less than a day. However, this is the first time they have attempted a project of this magnitude.

The company claims that their building method is environmentally efficient, reducing waste and greenhouse gas emissions.