This naturally-sourced hot spring is now home to a clothing-optional resort.

This modern antique shop is a museum for 1980's Saturday morning cartoon culture.

Paranormal experiences in this hotel's room 217 led Stephen King to write "The Shining."

Remants of foundations, streets, and streetcar tracks inhabit the cliffs where a landslide occurred in 1929.

A castle that was built stone by stone by an eccentric journalist.

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

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

A mosaic-tiled house built by graveyard sweeper Raymond Isidore.

These quaint French houses dangle precariously over a precipice.

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

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

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

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

This professional clown's home is an outsider art wonderland.

Beautiful carved tunnels.

This modern French ossuary contains the jumbled bones of 130,000 WWI soldiers.

Monsters and miniatures are held in equal esteem at this wondrous museum.

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

An icy lake tucked among jaw-dropping alpine panoramas.

Historic medieval fortified city in southwest France.

The largest underground church in Europe.

This historic island prison holds one of the dungeons from the Count of Monte Cristo even though it is a work of fiction.

Hundreds of hidden passageways weave through the old quarters of Lyon.

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