Neither Spanish settlers nor anyone since has been able to tell who built these strange California rock walls.

The recovered bones of martyrs slaughtered during The Terror are on display in this church crypt.

A popular shrine where the Blessed Virgin allegedly appeared in 1830, displaying a holy armchair and two incorruptible remains of Lady Saints.

This former “ante-chamber to the guillotine” has been refurbished to illustrate the brutal history of French justice.

Exquisite wall sculptures carved in secret by an early quarryman in an obscure corner of the Paris Catacombs.

The ruins of a Duke's bucolic dream, where camels once roamed alongside "Dutch" windmills and faux-Italian vineyards.

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

Down a cobblestone alleyway is a museum dedicated to Romanticism, with a secret garden.

"In the Dark" Restaurant in Paris offers dinner in complete darkness.

19th century pendulum and a clock restored by a rogue group of guerilla artists.

A mechanized clock where a man fights off a dragon, crab, and rooster.

The very center of Paris is surrounded by a bevy of strange good luck rituals.

A museum of carnival attractions where you are invited to ride the rides.

This massive library holds what was once the largest book collection in the world.

The macabre collection of Jacques Sirgent, an expert scholar on the undead and all of their trappings.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

An abandoned, desolate train tunnel that was used during World War II.

The heart of a Scottish legend had a centuries-long journey before reaching its final resting place.

This Scottish manor house is a lush relic from the life of a literary great.

The main gates have been locked since 1745 and will remain so until the Stuart Dynasty returns to the throne.

This huge concrete map of Scotland was built as a thank you gift from a Polish soldier.

Students can borrow artwork from this gallery to display in their own residences.

The graveyard with the highest IQ in Britain.