Hundreds of hidden passageways weave through the old quarters of Lyon.

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

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

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

The curious underground history of keeping Paris clean.

A grotto-like lodge decorated with gilded mosaics, rocks and a noisy waterfall was the setting for the most sumptuous pleasure house of 1900s Europe.

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

One of the greatest maze designer’s greatest mazes.

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

Science fiction's grandfather has a fittingly marvelous tomb.

Stroll through retro Paris while shopping for old postcards and discarded doll heads.

Behind the pink curtain, Au Bonheur du Jour, an art gallery of erotic archives.

A surrealist timepiece by the artist of melting clocks.

A scandalous Art Nouveau collaboration that set Paris all atwitter at the turn of the century.

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

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

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

A museum of magic with a Sadist past.

A counter-culture bookstore like no other hides in plain sight in the streets of Paris.

Walk upon the mementos of the dead in this Parisian courtyard paved with medieval tombstones.

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

The oldest stone house in Paris was built by its most famous alchemist.

The macabre collection of Jacques Sirgent, an expert scholar on the undead and all of their trappings.

Notorious artist squat renovated into legal studios.