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

The construction of a tram line unveiled hidden remnants of the old medieval city.

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

Stripes of human ashes cover a back lawn in the most sought-after burial grounds in Paris.

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

This medieval tower is all that remains of the castle where Joan of Arc was held before being burned at the stake.

What looks like a normal building is really a hollow facade hiding a subway vent.

An ancient monastery, a locked room, and a mysterious book heist.

Hundreds of secret cabinets built into the walls of legendary poisoner's private work room.

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

This French castle is said to have once held the Holy Grail but is now a gorgeous mountaintop ruin.

Sleep in a climate-controlled plastic bubble for the night.

This stunning French estate was so lavish that it landed its original owner in jail for the rest of his life.

Beautiful carved tunnels.

A well-preserved medieval village nested on a rocky outcrop and surrounded by a network of cliffs, natural bridges and canyons.

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

A French valley with forests so lush it was nicknamed "the Small Amazonia of the Pyrenees."

The headless bodies of more than 1,300 guillotined victims of the Reign of Terror are buried here in mass graves.

The largest underground church in Europe.

Historic medieval fortified city in southwest France.

Where the high court feasted, frolicked, and high courtesans put their royal lovers' diamonds to the test.

At Monet's beloved home you can still see the Japanese bridge, waterlilies, and weeping willows that were the subjects of some of his most iconic paintings.

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

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