Croatia's "hairy stone" fortress is one of the most well preserved Istrian castles.

A self-proclaimed libertarian micro-state on a tiny bit of disputed territory between Serbia and Croatia.

A tower marking the spot where Yugoslavia began its resistance against the invading Nazis stands neglected, but not quite forgotten.

When Croatia became independent of Yugoslavia, the splintering governments left behind these concrete tunnels.

Museum devoted to the artificial language of Esperanto.

This museum promotes informed contraception by documenting its often secret past.

The resting place for anonymous victims of the Danube's dark waters.

The great Danube river starts here.

A Black Forest cuckoo clock theme park features one timepiece big enough to walk inside.

This former steel and coal plant is now a neon-lit industrial fantasia.

Largest illuminated advertisement sign in the world.

This cubist Vienna church building looks like some sort of alien stonehenge.

Enter the cabin of a life-sized Hindenburg replica.

Striking occult iconography on a medieval German church.

An extraordinary mechanical calculator designed by the mathematician and philosopher Gottfried Leibniz.

Two nations form a rare four-sided border at the peak of a mountain, philosophical questions result.

Art and a pun, all in one.

The man who gave his name to magnetic measurement is buried in the city where he did his best work.

A former Nazi lookout tower with a magnificent view of the Rhineland.

The birthplace of an eccentric alchemist and possible inspiration for the fictional reanimator of monsters.

The largest free-standing aquarium in the world resides in a hotel lobby in Berlin.

After years of being casually peed on by humans, this tree is peeing back.

Someone loved this song enough to carve all of its lyrics onto a tree trunk in a Berlin park.

A stairway to heaven, or to nowhere at all.