One of the entrance to the Underground City in Beijing.
Every able-bodied men, even school children, took part in the effort.
Centuries-old city walls and towers that once circled ancient Beijing were cannibalized for supplying construction materials for the complex.
All this, however, came to naught.
The Sino-Soviet split of the 1950s and 60s also lost political importance.
Photo credit: Sim Chi Yin
The government still considered underground bomb shelters an essential requirement in cities.
This led to the proliferation of for-profit underground housing.
The management of these buildings is acomplicated systeminvolving a number of middlemen.
The locals call them rat tribe or shuzu.
In 2015, thousands of residentswere evictedfrom their underground housing.
In 2017, authoritiesdiscovered400 people living underneath an upscale Beijing apartment complex.
These photographs were taken by Chinese visual artist and documentary photographer Sim Chi Yin.
Wei Kuan is an insurance salesman by day and a member of the rat tribe at night.
Photo credit: Sim Chi Yin
Chang Wanle works as a taxi driver.
Photo credit: Sim Chi Yin
Chen Laxiu and her husband works on the subway cleaning stops.
Their room measures 6 feet 2 inches by 7 feet 10 inches.
He is in charge of 72 rooms and about 100 inhabitants.
He himself lives in one of the rooms.
Photo credit: Sim Chi Yin
