These crumbling Nazi artillery bunkers are now fair game for massive graffiti projects.

The vast chamber inside this abandoned cooling tower looks like something out of a sci-fi dystopia.

Lavish royal estate punctuated with heated greenhouses.

An abandoned saucer-shaped monument in the Bulgarian mountains.

A giant bug impaled on a 75-foot-tall needle.

Climb inside an iron crystal magnified 165 billion times its normal size.

A Cold War command center is hidden under an idyllic countryside.

This ghost town in Belgium will lose its street art when it ceases to exist.

This annual Belgian water race attracts bathtub captains from all over the world.

An open-air sewer system that was covered piece-by-piece over 300 years.

This sprawling Belgian fort was once thought of as impenetrable but now it is simply an abandoned relic.

This giant urban staircase was built to keep the city's brave fighting men from getting waylaid in the red light district.

An eerie, derelict amusement park in Berlin.

A surreal museum of extraordinary industrial objects.

Super-heavy Nazi architectural experiment.

Hungarian self-built castle.

Macabre astrological automaton clock dating to the late 1400s.

A whimsical and twisted animatronic monster tour beneath the streets of Berlin.

Berlin's old airport.

Dummies recreate radiological discoveries from history.

One of the deepest indoor swimming pools in the world.

The remains of a sunken military ship wreck visible through clear water.

Yugoslavia's biggest underground airport lies in ruins.