Terrifying derelict military hospital once housed a recuperating Hitler.

An eerie, derelict amusement park in Berlin.

This abandoned coliseum was intended to be a grand Nazi rallying ground before it was halted at the end of the war.

Hitler's bleak vision of relaxation still stands as a mostly abandoned 10,000-room resort complex.

A crumbling bakery where forced laborers from the nearby concentration camp toiled to feed their fellow prisoners and Nazi soldiers.

This historic cemetery was inaccessible for several years due to dozens of land mines.

A war-torn Olympic relic is being overtaken by graffiti and nature.

Imperial palace of Emperor Galerius, the Emperor behind the worst Christian persecutions during the Roman Empire.

Near Belgrade, an ancient-looking sarcophagus serves as a World War I monument.

This outcropping was once home to a medieval monastery destroyed during the Ottoman conquest.

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

Nikola Tesla's ashes are held in a golden sphere, surrounded by his works.

Structure built from the skulls of vanquished foes.

A misnamed well, with a deep dark past.

Ride in 1960s style on the private luxury train Marshal Josip Tito used to travel around Yugoslavia.

A pair of connected skyscrapers form this symbolic gateway.

An eerie collection of the surviving structures from a past celebration of the future.

A New York–based physician returned home to Spain to build his own elaborate monument to Christopher Columbus.

The remains of the second-oldest zoo in Europe can be seen within these library gardens.

Over two centuries old and counting, Madrid's massive botanical garden contains one of Europe's only desert environments.

The defensive tower was built centuries ago to warn locals of Berber pirate attacks.

These abandoned country fairgrounds are filled with replicas of Spanish monuments.

Barcelona's only remaining tram system takes riders to the Tibidabo funicular.

These secluded and abandoned anti-aircraft defenses have become one the most scenic viewpoints in Barcelona.