Hundreds of prehistoric stones, arranged in perfect lines in a French field.

The world's tallest bridge is also possibly the most elegant.

This ancient theater was once the home of fierce gladiatorial battles.

This collection of French root art looks like an indoor fairy wonderland.

The Cimetière des Chiens et Autres Animaux Domestiques is one of the oldest pet cemeteries in the world.

The 16th-century church was kept in its ruined state as a reminder of the casualties of World War I.

Hundreds of secret cabinets built into the walls of legendary poisoner's private work room.

An ancient monastery, a locked room, and a mysterious book heist.

The sunken structure looks like the victim of a catastrophic flood.

A self-built mosaic house and sculpture park.

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

A medieval church with largest and oldest collection of Renaissance frescoes in France.

This medieval tower is all that remains of the castle where Joan of Arc was held before being burned at the stake.

There has been an astronomical clock on this spot since the 14th century.

This French castle is said to have once held the Holy Grail but is now a gorgeous mountaintop ruin.

Museum in a swimming pool where the water still flows.

Ghosts of France's colonial past.

The only remaining collection of flayed figures made by French "madman" Honoré Fragonard.

A beautiful and classically designed villa, with an hourly infestation of monsters.

The world's largest reflecting pool is just two centimeters deep.

A mosaic-tiled house built by graveyard sweeper Raymond Isidore.

Two small chapels housed inside an ancient tree.

An enchanting work of outsider art, full of whimsical sculptures and carvings.

This modern French ossuary contains the jumbled bones of 130,000 WWI soldiers.