One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

The hidden ruins of an old hydroelectric plant reclaimed by nature.

One of the most spectacular bridges in Spain spans a narrow chasm that divides the city of Ronda.

Three bridges and one giant canyon make up this fantastic Spanish settlement.

The final resting place for a wealthy Roman family, this tomb might be the best preserved of its kind outside Italy.

A sixth-century Byzantine cistern hidden below a modern carpet store.

Legend says if you stick your thumb in the hole and it gets wet your wish will be granted.

A small etching on the white marble parapet was written in runic script by a Viking mercenary.

Replicas of Apollo's leonine stone guard cats still line a sacred row in Greece.

Giant marble phalluses on the sacred island of antiquity.

A Museum of Psychiatry in a still-operating mental institution.

This fairytale castle was built as a show of power but was nearly torn down thanks to its history of torture.

This statue dedicated to the story of a Flemish boy and his dog was relatively obscure in Belgium, but a cult sensation in Japan.

Most prolific publishing house in the 1600s open to the public.

Rare wooden escalators lead deep down into an otherwise staggeringly monotonous tiled tunnel.

This monolithic slab of art metal crowns a German slag heap.

The Bauhaus-style former industrial complex is considered the world's most beautiful coal mine.

The largest mosque in Germany.

An industrial relic is now one of Europe's most staggering art spaces.

Also known as the Blue Church, the building was consecrated to the daughter of Andrew II.

Baroque celebration of the end of the Great Plague of Vienna.

This unique Lady Liberty is one of the only examples of the figure sitting down.

Monumental sculptures guard many of the graves, transforming this necropolis into an open-air fine art museum.

Packed to the ceiling with antique taxidermy and hunting arms.