Here's some chilling photos of a few of those empty cities:
http://www.businessinsider.com/these-chinese-cities-are-ghos...
http://www.businessinsider.com/these-chinese-cities-are-ghos...
http://www.forbes.com/sites/wadeshepard/2016/04/23/chinas-la...
Sounds like they build them first then move in the people. Probably cheaper and faster that way? They do have 1.3 billion people.