The largest of these is Kangbashi in northern China. Built for a million people about ten years ago, it's inhabited only by about a tenth of that number.
(note - links corrected)
Years ago, I discovered China's urbanizing drive, their "ghost cities," and their empty towns: staggering amounts of money were invested to develop them, yet almost no one lived there.
Years later, and they haven't changed much. (Here's a recent update on Kangbashi.)
Other countries have their stories of enormous expenditure, followed by emptiness or failure. Check out the gorgeous, expensive Forest City of Malaysia--empty and eerie for the few who do go there: