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

An ancient ossuary in Rouen.

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

135 bronze medallions mark a French meridian line which once rivaled the hotshot Greenwich timeline.

England's most notorious suicide spot.

These stark white cliffs were spat up by the sea and are slowly being retaken by it.

This massive library holds what was once the largest book collection in the world.

A small world of mechanical magic and metal merry-go-rounds in a Outsider art Museum.

From carts to cars, this leftover Roman bridge in France has managed to survive for centuries.

Balconies that have a most unusual accent.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

Remains of Roman amphitheater hidden in a sleepy quarter of Paris.

Medieval museum built over Roman baths that features famous tapestries of a lady and a unicorn.

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

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

The mummified heart of Louis XVII, the lost dauphin of the French Revolution.

One woman's decades-long obsession with the "La Fée Verte."

A Parisian cemetery where the elite and artistic are interred beneath an eccentric collection of tombs.

Abandoned railway line circling the city of Paris.

Historic medieval fortified city in southwest France.

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

The vast, legendary catacombs hold secrets much stranger than stacked bones.

A 14th century bridge built as a fortress, where the devil lurks on one of its towers.

Africa's Venice on stilts.