Go inside to really appreciate this 500-year-old technological masterpiece.

This 2,000-year-old Doric bridge is still open to pedestrian traffic to this day.

Ruins of a German castle on top of a towering stone pillar.

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

This strategic isle was once swapped between empires and almost entirely destroyed in a bomb explosion.

This Dresden church was purposely rebuilt Protestant after being demolished in World War II.

The bells remain in a shattered heap exactly as they fell when the church was bombed in World War II.

A memorial to a Swedish hockey player's "encounter" with aliens.

A whimsical sculpture garden right out of a children's storybook.

The deepest metro station in the world.

When you've got to go, you've got to go.

340-foot statue built to honour the Heroes of the Soviet Union.

It houses the remains of a 17th-century version of the Titanic.

A marvel of Byzantine engineering under the streets of Istanbul.

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

Despite attempts by local police to discourage it, Beatles-inspired graffiti has been a means for artists to air grievances for decades.

This bridge was constructed from the rubble of the infamous Bastille.

Six ravens are kept captive (but well-fed) at the Tower of London to prevent the fall of the Crown.

London's last remaining public soapbox site has seen speeches from Karl Marx, Vladmir Lenin, and George Orwell.

This tipsy office building in downtown Prague was originally called “Fred and Ginger.”

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

Eighty million natural history specimens call this gargantuan museum home.

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

France's most famous cemetery, with some of its most curious tombs.