Leaking natural gas never stops burning on this hill, making it an infinite inferno.

Colorful mineral deposits turn these mountains into an Impressionist fantasy.

Mirrors and glass shards cover every inch of this arrestingly beautiful mosque.

Putrefaction plateaus in Iran, where the dead were sent for decontamination before going to their final resting place.

This ancient structure is widely thought to be the oldest intact pyramid in the world.

An abandoned outdoor movie theater in the Sinai desert.

This entire town moved to a safe location after it was devastated by an earthquake, but the remains of the original town are still around.

"Stairs of the Turks", a chalky white cliff eroded conveniently into stairs, allowing for easy pillaging.

Small on the outside, big on the inside, this church is an astonishing act of visual deception.

A beautiful but toxic fountain of mercury.

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

The beauty and the beast of hydraulic mining is on full display at this California Historic State Park.

Barcelona's historic 19th-century sewers, whose foundations were laid in medieval times, are open to the public for exploring.

This semi-secret storybook hedge maze is also the oldest garden in the city.

France's most famous cemetery, with some of its most curious tombs.

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

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

Where Aleister Crowley taught magick in "La Chambre Des Cauchemars," his "Chamber of Nightmares."