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

Spanish architects used seized Muslim gravestones to rebuild parts of the fortress.

Extremely famous in his native country, this Cracovian painter is all but unknown beyond Polish borders.

The oldest and smallest cemetery in Paris is only open to the public twice a year.

This giant metal cross perched atop a mountain can only be reached by foot.

These unique markers designate the route American forces took during the Liberation of France.

This museum houses an imposing skeleton army comprised of creatures great and small.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

A unique seaside cave where Aleister Crowley faked his own death.

An ancient and majestic fortress that played an integral role in Portugal's road to independence.

This unreal Portuguese palace looks as though it's made from a pile of different castles.

One man's remarkable private collection of art from around the world.

The best place in the world to buy tinned fish.

One of the smallest bookstores on the planet.

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

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

Elaborately carved to showcase the glorious wealth that the age of exploration brought to the Portuguese empire.

Erotic art covers the walls of the largest ancient pleasure palace.

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

This amazingly well-preserved villa just outside Pompeii boasts rare examples of ancient Roman paintings.

The walls and streets of the ancient city are peppered with penises.

Ancient snack bar of the Roman Empire re-opened.

This massive monument has been telling the time for 150 years—at a slight angle.