Two small chapels housed inside an ancient tree.

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

A Gothic cathedral created from volcanic rocks.

The famous winding walk at Chartres is surrounded in mystery and myth.

Pitié-Salpêtrière was the dumping grounds for women who received the dreaded diagnosis of "hysterical."

The largest underground church in Europe.

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

This massive blockhead sculpture hides an entire library.

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

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

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

This charming cobbled backstreet is the most Instagramable street in Paris, much to the residents' annoyance.

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

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