A Nazi concentration camp and Anne Frank's place of death.

Stalactites and stalagmites in a beautifully lit cave.

Windblown rock formations in an ancient Roman quarry.

An ancient aqueduct tells the story of Sardinia's ancient Roman past.

This Arabesque Italian castle was built with a primitive, if ingenious, air-conditioning system.

This triumphal 16th-century arched gateway leads to the oldest street in Palermo.

Where Aleister Crowley taught magick in "La Chambre Des Cauchemars," his "Chamber of Nightmares."

142 ceramic steps become a mosaic once a year.

"Stairs of the Turks", a chalky white cliff eroded conveniently into stairs, allowing for easy pillaging.

Once a granite mine, this beautiful lake is the perfect place to cliff jump and zipline in Denmark

Northern Europe’s largest castle ruins sit precariously on an island cliffside.

The largest of Denmark's seven mysterious round churches stands on an island in the Baltic Sea.

This remote island, home to the easternmost point in Denmark, once hosted pirates and a military fortress.

One of the most easily accessible examples of the rare 1960s UFO houses.

This poignant tribute to the White Rose movement showcases artifacts related to the heroic anti-Nazi struggle.

Go surfing on this urban wave, "hacked" by local surfers.

This magnificent museum claims to house the cranium of a disciple and the skull of a pope.

Golden cobblestones remember a time when this small alley was used to avoid having to give a Nazi salute.

The footprint of a frustrated devil in Munich's Cathedral.

Daily jousts and dancing barrel makers in Munich's mechanical clock.

A fearsome dragon clings to a corner of Munich's city hall.

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

Art historians have debated the identity of this medieval stone rider since the 19th century.

A museum that chronicles the history of the Nuremberg Trials for Nazi war criminals in the building where the trials were once held.