The Underground City of Beijing, also known as the Underground Great Wall, is a Cold War-era bomb shelter located beneath the city of Beijing, China. This vast network of tunnels was constructed for military defense, providing a hidden infrastructure capable of housing and transporting intercontinental ballistic missiles (ICBMs). The complex spans over 3,000 miles (5,000 kilometers), showcasing the extensive efforts made by China during the Cold War to ensure the protection and mobility of its nuclear arsenal.
Although primarily a defensive structure, the Underground City also served as a shelter for the civilian population in the event of a nuclear attack, highlighting its dual-purpose design. The construction of such a massive underground network reflects the strategic importance placed on nuclear deterrence and the protection of key military assets during this period.