An ancient ossuary in Rouen.

This narrow path was cut right into a French mountainside to feed the country's early naval expansion.

Underneath a chalk hill in France lies what Hitler hoped would be the underground launching base for a devastating new weapon.

Located in the house where Gustave Flaubert was born, this odd museum has more to do with medical grotesquery than the Western novel.

The historic Masonic Lodge in which the first-ever female Mason was initiated.

Figures of unknown origin carved into the surfaces of underground caves.

This futuristic observatory at the top of the Pyrénées offers unrivaled views.

A quaint medieval millhouse hovers surprisingly above the waters of the Seine.

Former hunting lodge of a duke who was an avid collector of impressionist works.

Perhaps the most beautiful of preserved saints, with a little help from Paris.

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

A unique underground structure dating back to the 1st century BC.

The remaining relics of the patroness of Paris lie in a chapel under a striking double spiral staircase.

This bridge was constructed from the rubble of the infamous Bastille.

The deserted pirate-themed restaurant still entices explorers.

This submersible road connecting a French island to the mainland is lined with safety towers for when the tide strands travelers.

These crumbling Nazi artillery bunkers are now fair game for massive graffiti projects.

A swath of France so devastated by war it is still forbidden to go there.

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

A colossal sculptural lion built by the same man who designed the Statue of Liberty.

A centuries-old complex of hand-dug stone chambers has sheltered locals in times of trouble.

The Argonaute submarine was the French navy's pride and joy in the 1950's.

One of the world's most complex timepieces.

The Church of the Annunciation was carved into the face of a cliff, just like the rest of the town of Haute-Isle.