Between 1984 and 2010, the amount of built-up areas in China increased from 3,413 square miles to 16,126 square miles, the Asian country used more concrete between 2011 and 2013 than the one used by US in the 20th Century. But there is a negative phenomenon: Zombie factories and unborn cities. 

The rate of development has overtaken demand in China. The BBC reports that faced with falling prices and sales, the government has had to step in to cut back some industries. In Hebei, the impact has been hard, many of its state-owned plants have been shut down and remain empty. 

The same fate has happened in many places, creating "zombie factories" across the country. The shift from industries like steel production to telecommunications, electronics and biotechnology has been fast. Europe and the US underwent a similar shift over several decades, China's shift took just a few years.

Many urban areas have become ghost cities

In Changzhi and Luliang, in the northern province of Shanxi, the shells of cement factories that could not survive lie empty. Factories that once employed more than 1,000 workers now function with fewer than 100. In China, many urban areas have become "ghost cities", they have been left unoccupied when the expected rush of inhabitants from the countryside never appeared.

Kangbashi, a new district in the city of Ordos, could house 300,000 people but only 10% of its residences are occupied. Entire apartment blocks, shopping centres, plazas and parkland lie empty, waiting for their residents to arrive.

The photographer Kai Caemmerer has been documenting some of the empty cities in China. He thinks part of what makes these places seem so weird is the speed with which they have been built. 

The government has said it intends to move 100 million people from rural parts of the country into cities by 2020. This coordinated migration could fill at least some of the vacant cities in China.