Site of one of World War I's most horrific scenes.

Legend has it this 11th-century castle was paid a visit from the devil.

One architect's organic, human-centric design has been fully realized in this alien art house.

100-windowed castle turned art gallery, built by one dedicated mason.

The world's most famous cheese caves.

Lyon, France is home to two remarkably preserved Roman theaters, one dating back to 15 BCE.

One man's desire to transcend art led to the construction of this outsider chapel.

This French "sea of rocks" is packed with stunning rock formations and its own medieval castle.

This modern museum of Mediterranean culture is surrounded by a surreal concrete honeycomb.

From carts to cars, this leftover Roman bridge in France has managed to survive for centuries.

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

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

These medieval ruins have survived since the 12th century, even providing shelter from the Nazis.

An abandoned beach resort in Normandy reclaimed by artists.

The remains of 40,000 humans, meticulously stacked in a tiny churchyard shed.

Series of underground houses inhabited continuously for centuries.

Even France's favorite aquatic son Jacques Cousteau, couldn't get to the bottom of it.

The spiral staircase hidden inside this giant Parisian column was likely built for Catherine de Medici's astrologer.

This salt marsh in Southern France is as pink as the flamingos that inhabit it.

The post-apocalyptic remnants of a bucolic town ruined by a plane crash.

Since ancient times these picturesque springs have been providing bathers with healing waters.

An architectural oddity of six stories, accessed by graceful ramps.

Despite centuries of architectural innovation, this French castle is being built like it's the 13th century.

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