Sunny Peninsula, a seaside development in the southern Chinese city of Guangzhou, was supposed to house 5,000 families in dozens of towers spread across an area the size of 30 soccer fields. Many of the buyers were white-collar workers benefiting from the fastest urbanization in human history.

But the project now looks more like the set of a disaster movie. Half-finished apartment blocks stand empty and abandoned. Untouched for months in the humid summer weather, piles of rebar and steel beams are accumulating coatings of rust.