Hitler's last secret is a sprawling underground headquarters in a remote region of Poland, at Ksiaz Castle. It has a network of underground complexes in the Owl Mountains.

The greatest hideout in fascist Italy's history: the Monte Soratte bunker. It is built directly into a mountainside with security features even a Bond villain could only dream of.

Infamous for his bunkers constructed during World War II and throughout the Cold War, Stalin's hideouts have maintained a shroud of secrecy for decades.

Ukrainian dictator Viktor Yanukovych, steals billions and hides his treasure trove in a mind-bending corruption scheme that leads to Mezhyhirya.

The People's Palace in Bucharest, a colossal remnant of Ceausescu's regime, sinks slightly each year under its own weight. Rumours of a vast underground bunker network beneath it continue to intrigue, though remain unverified.

Following the cutting of Albania's ties with its allies, Enver Hoxha drove his country into geopolitical isolation. This accelerated his paranoid notions of an imminent invasion and threat to his rule.