Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

Humble beginnings for one of the world's most famous scientists.

This huge metal monument is slowly being stripped to its concrete skeleton.

Yugoslavia's biggest underground airport lies in ruins.

This abandoned Croatian stronghold never saw a great deal of conflict but it is still a beloved relic nonetheless.

This Japanese-inspired labyrinth of hot springs is hidden in a Chilean forest.

When Croatia became independent of Yugoslavia, the splintering governments left behind these concrete tunnels.

Longest fortress system anywhere in Europe.

A futuristic, brutalist masterpiece that is also strangely prison-like.

A curious cave church carved into the face of a cliff.

This museum preserves the hand-dug tunnel that kept Sarajevo afloat during the Serbian siege.

A Red Cross memorial museum at the site of the Niš concentration camp that operated for four eventful years during World War II.

This memorial park stands on the site of one of the largest mass executions of the Second World War.

The bizarre rocks of Đavolja Varoš are the result of natural erosion.

This 14th century castle withstood years of battle but is now sliding off the hills into the Danube.

This spaceship-like Serbian monument reaches for the stars in celebration of the fallen fighters of fascism.

Giant marble phalluses on the sacred island of antiquity.

Hideout of thieves, monks, and goat-footed gods.

Monasteries on rock pillars, once accessible only by frayed ropes.

A Bulgarian monument to Russia's role in World War II is constantly being painted in pop culture protest.

A spectacular Bulgarian cave resembling a devil's head with a waterfall rushing down its throat.

An ancient Thracian city where fire rituals were practiced on the largest cult altar in Southeast Europe.

This massive stone and steel monument remembers a century-old battle that cost thousands of lives and nearly destroyed the city.

This once-grandiose behemoth of a monument from the socialist era now sits quiet and closed up.