We went to the Beijing Underground City. The girl next to Mackenzie was our guide through the approved tourist section. This complex is a relic of the Sino-Soviet border conflict in 1969 over Zhenbao Island in northeast China’s Heilongjiang River, a time when chairman Mao Zedong ordered the construction of subterranean bomb shelters in case of nuclear attack. The tunnels, built from 1969 to 1979 by more than 300,000 local citizens and even school children, wind for over 30 kilometers and cover an area of 85 square kilometers eight to eighteen meters under the surface. It includes around a thousand anti-air raid structures. In the event of attack, the plan was to house forty percent of the capital’s population underground and for the remainder to move to neighboring hills, and it is said that every residence once had a secret trapdoor nearby leading to the tunnels.