The Pyongyang Metro
The Pyongyang metro can be described as a typical socialist subway. Some lines are more than 100 meters deep underground. The idea behind that is to use the metro tunnels as fallout shelters in case of war. Staff of the Metro wear military-style uniforms that are specific to the metro workers.
Similar to the legendary Metro 2 in Moscow, the Pyongyang metro has two generally-unknown facilities: 1. An "underground square" a space for storing soldiers and equipment during war and a command post for the army leadership.
2. An "underground road" between the subway stations, linking the airport to the presidential palace to evacuate the great leader in case of war.