The Beijing Underground City is a Cold War-era bomb shelter network located beneath Beijing, China. Built during the 1970s amid tensions with the Soviet Union, this extensive tunnel system was designed to shelter up to 40% of the city's population in case of nuclear attack. The underground complex spans an estimated 85 square kilometers and includes facilities such as hospitals, schools, theaters, and even factories, all connected by a network of tunnels that could accommodate thousands of people.
The shelter system, also known as the Underground Great Wall, represents one of the largest civil defense projects of the Cold War era. While parts of the complex have been opened to tourists in recent years, much of it remains closed to the public and its full extent is still not completely mapped. The tunnels were constructed by hand by local citizens and reportedly could support life underground for up to four months in the event of a nuclear strike.