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

An icy lake tucked among jaw-dropping alpine panoramas.

Ghosts of France's colonial past.

Historic medieval fortified city in southwest France.

The mental institution where Van Gogh created some of his most famous work now allows guests to walk in the artist's footsteps.

This historic island prison holds one of the dungeons from the Count of Monte Cristo even though it is a work of fiction.

Two small chapels housed inside an ancient tree.

A Gothic cathedral created from volcanic rocks.

This natural French spring has been turned into a magical grotto by Roman and medieval constructions.

Do these monsters look familiar? The gargoyles on this church are all from pop culture.

The largest underground church in Europe.

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

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

The first green space constructed on an elevated viaduct.

A cave dwelling that was started by the Celts, expanded by monks, and finished by knights.

Ancient paintings known as the "Sistine Chapel of Cave Art."

Sacked by Vikings, blessed by William the Conqueror, dealt a fatal blow during the French Revolution—these ruins have seen it all.

This French ghost town from World War II has been left as a memorial to German atrocities during World War II.

This whimsical castle of grottoes was the labor of love of a French postman, and one of the greatest achievements of outsider architecture.

An off-the-beaten-path boutique stuffed with an eclectic collection of upcycled goods.

Architect Le Corbusier built his friend a cubist house to match his impressive collection of cubist art.

An overlooked marble is the only surviving in-place 18th century example of the measurement that changed how we define distance.

This Parisian café sticks almost exclusively to an ethos of reuse.

A subterranean shelter remains intact under a busy Paris railway station.