Moscow Metro-2
The Russian government has neither confirmed nor denied the existence of this underground metro system. It was supposedly constructed during Joseph Stalin’s reign. Allegedly code-named D-6 by the KGB, it is rumored to connect the Kremlin with the Federal Security Service headquarters, the government airport, and an underground town at Ramenki. In 1994, an urban exploration group discovered the underground entrance to the rail system. Ten years later, former Soviet adviser Vladimir Shevchenko finally confirmed the facility’s existence.