2 – Moscow Metro-2, Russia

If nuclear catastrophe or epic natural disaster strikes Russia, they’ve got it covered. Welcome to the city beneath a city, Moscow’s purported secret underground system, a series of metro lines linking the Kremlin, the Federal Security Office HQ, the government airport and several other important locations. Reportedly built by the KGB, the existence of this complex labyrinth hasn’t been formally admitted to by Russia but its rumoured that Stalin’s extreme paranoia was the catalyst for its construction.