The 7,000-year-old calcium carbonate formation creates a magnificent natural bridge.

Outsider art meets hard scrabble mountain life in this woodcarver's home/art piece.

A medieval bridge stretches over a sulfur-rich river that leads to year-round natural hot springs.

The natural hot spring that was integral to the creation of Canada's first national park.

For centuries, this town's hot springs have been embraced by rich and poor—and even by Popes.

Trick water gardens from 1619 featuring a 200 piece mechanical theater powered by water.

Everything in this miniature world was handmade from matches, paperclips, wires, tin cans, and other everyday objects.

An ever-growing collection of rare and strange objects owned by local Arkansas illusionist Maxwell Blade.

This cascade of mineral-rich hot springs and waterfalls is an oasis in the Jordanian desert.

One of the last free public hot springs is decorated with hippie art.

Volcanic rocks ground down into sand make this Spanish beach as black as night.

One of the largest caves in the world open to the public.

This was the second largest mercury mine in the world and one of the oldest preserved mine complexes in Europe.

Deep underground, the rusting remains of a German water pumping station from World War II.

This massive subterranean fissure is known as the "underground Grand Canyon."

Apparently, Hell has waterfalls in Slovenia.

A miniature train-ride through Slovenia's largest cave system.

This quaint farm in the Peloponnese countryside hides an astonishing cache of antique curiosities.

Nicknamed the "Museum of Horrors," this French anatomical collection has been fascinating visitors for over a century.

At this monastery, monks make raw-milk cheese and use excess whey to create methane that powers their hot-water system.

One of the greatest maze designer’s greatest mazes.

An ethereal glowing blue ocean cave in Croatia.

A wonderfully strange collection of 500+ stuffed frogs doing people things.

This Peruvian canyon is filled with geometric salt pools that have been being harvested since the Incan empire.