Two small chapels housed inside an ancient tree.

The largest underground church in Europe.

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

In the best of all possible worlds, everyone will get a chance to see this statue in which Voltaire's heart is interred.

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

This former “ante-chamber to the guillotine” has been refurbished to illustrate the brutal history of French justice.

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

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

This statue was given to France by the United States to commemorate the centennial of the French Revolution.

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

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

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

One of the oldest medical collections in Europe focusing on rare surgical instruments.

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

Abandoned railway line circling the city of Paris.

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

Indents in the pavement are all that remain from a grisly death machine in Paris.