One of the smallest bookstores on the planet.

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

A museum dedicated to the centuries-old cave dwellings that housed marginalized communities on the outskirts of the former capital of Muslim Spain.

Mysterious texts covered in mystical symbols were found in caves at this site centuries ago.

Spain's unique Mosque-Cathedral has been a place of worship for both Muslims and Christians throughout its history.

A curious carving hides on a marble column in the Mosque-Cathedral of Córdoba.

This medieval synagogue survived the Inquisition as a hospital and church.

One of the oldest suspension bridges in the world blends in perfectly with a medieval castle.

A former fisherman's hut deemed too small for habitation is now a delightful tourist draw.

This Welsh village gave itself a ridiculous name in a publicity stunt a century ahead of its time.

More than 5,000 artifacts donated by the people of the city, plus a room entirely devoted to the band U2.

Tiny silver and copper fish set inside blue-green lights are like windows to the underwater world.

The last Victorian market in Belfast.

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

The ruins of this medieval castle in Northern Ireland have inspired artists from C.S. Lewis to Led Zeppelin.

A museum on the history of Paris, including a set of Napoleon's toiletries, Proust's room, and relics of the Revolution.

The remnants of a 1849 sunken ship lie underneath a building.

These concrete crustaceans are actually public restrooms.

A charmingly old-fashioned reminder of the historic building's former life.

A memorial to Wellington's well-loved, well-traveled wharf dog.

Inside this faux cave, visitors can learn how some of their favorite fantasy characters were created.

For more than a century, revolutionary graffiti has marked the wall of a Parisian church.

A horde of stray cats rule in this secluded Parisian cemetery under a bridge.

This aluminum “stairway to heaven” has impaled at least a couple of birds.