French commune at the heart of conspiracies.

The opulent home that inspired Tintin's Marlinspike Hall and the adventures within.

Green labyrinth formed by a karstic maze hidden in a preserved oak forest.

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

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

A massive, secret marina for the Nazis' most formidable weapon in the Atlantic.

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

The birthplace of the ferocious William the Conqueror, this castle is awash in medieval history.

One of the world's most complex timepieces.

This otherworldly French waterfall looks like its waters have turned to stone.

This crumbling, graffiti-covered mansion sits tantalizingly within reach of the proletariat who frequent a public park.

Tables of secondhand books fill the inner courtyard of this 17th-century stock exchange.

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

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

Miles of man-made caves and tunnels are currently used for cultivating mushrooms.

This recessed garden protects thousands of mountain plants by creating its own microclimates.

Bits of architecture from a town destroyed in World War I now decorate this hotel garden.

An art world insider finds himself battling for his artistic home.

Trek into the depths of the cave where 17,000-year-old paintings exist alongside 400-year-old graffiti.

A French library that makes sure its love of books is writ large... giant in fact.

Statue of a decomposing prince that once held his heart in its hand.

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

If they push on just the right spot, even the weakest person can move this titanic boulder.

Once a 19th-century brasserie, this McDonald's exterior celebrates Alsatian design and the "King of Beer."