The oldest stone house in Paris was built by its most famous alchemist.

One man has carved a number of natural New Mexico caves into psychedelic sandstone temples.

This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

This futuristic German spa allows visitors to float in a pool of salt water while zoning out to underwater techno.

This secluded aqua waterfall in the Grand Canyon is the perfect swimming hole, and the Havasupai tribe's fiercely protected natural wonder.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

Medicinal spa created with the discharge from a geothermal energy plant.

Dramatic river bend surrounds a natural red-rocked pedestal.

A 140-year-old castle with underground caves hidden in San Francisco.

An emerald-green grotto just a short trip from Austin.

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.

The history of occult science is turned into a creepshow at this lurid Prague tourist attraction.

A collision of human error and natural geothermal pressure created this rainbow-colored geologic wonder.

This jaw-dropping 19th-century bridge uses its reflection to form what appears to be a perfect circle.

Most-visited and most-photographed slot canyon in the American Southwest.

The mysterious, fantastical woodland inspiration for "The Lord of the Rings."

The sound of swaying stalks in this stunning grove has been named a governmentally recognized sound.

Rippling sand dunes frozen in the Arizona rock.

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

Stepping away from the glitz of mobsters and casinos to learn about the other history of Vegas.

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