A neighborhood church's unusual abstract stained glass was the final project of avant-garde artist Jean Cocteau.

Vienna's diversity-themed traffic lights were inspired by the Eurovision Song Contest.

A bike traffic circle showcasing the works of local graffiti artists.

These giant yellow bowling pins seem to be defying gravity.

An early 20th-century sanatorium, long abandoned and now being reclaimed by nature.

Hiding the longest subterranean river known in the world.

This centuries-old gothic monster has been converted into a sprawling, glossy bookstore.

This historical Netherlands fortress still bears the marks of its single siege.

Incredible labyrinth of man made caves.

Two gravestones clasp hands over the religious divide.

Cold war icon and onetime "hole" in the iron curtain.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

A monument to the three wars that led to German unification towers within a Berlin traffic circle.

Metro station with a claim to rock n' roll fame.

An imperial church bombed to ruins during WWII now stands as a jagged memorial.

The last remnants of a massive medieval wall that once encompassed the city of Berlin.