Hitler's last secret is revealed to be a sprawling underground headquarters in a remote region of Poland, at Ksiaz Castle, complete with a network of underground complexes in the Owl Mountains.

The greatest hideout in fascist Italy's history: The Monte Soratte Bunker. 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, uncovering the extent of the fortifications meant to secure Stalin from the threats of the West.

Having stolen billions from the populace, Ukrainian dictator Viktor Yanukovych 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, further fuelling his paranoid notions of an imminent invasion and threat to his rule.