A beautiful geyser under environmental threat.

Here, at the "world's longest art gallery," you'll find forty miles of ancient petroglyphs and pictographs.

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

Crystal clear lake with a shoreline of travertine located in a Colorado canyon.

Under the right circumstances, this waterfall in Yosemite briefly turns a luminescent fiery orange.

A roaring, awe-inspiring double cascade of icy water flows through woodland Oregon like something out of a Tolkien novel.

For two weeks every June, fireflies in the Smoky Mountains perform an astonishing light show.

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

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

Bring your own cardboard to the slippery slopes of concrete hidden in a neighborhood park.

Rippling sand dunes frozen in the Arizona rock.

Harry Potter once visited this massive limestone cliff, which was carved by an ancient glacial river.

The forest that inspired Winnie-the-Pooh's Hundred Acre Wood can be found outside London.

This short bridge is the only thing connecting a tiny Irish island to the mainland.

The largest cave chamber in Britain—big enough to fit a whole cathedral inside.

Fascinating town where normal life interfaces with the occult.

A subterranean playground in an abandoned slate mine.

This tangled English forest looks like something right out of a fairytale.

Northern Ireland's Brobdingnagian stepping stones.

The hidden "ballroom" under a mansion lake was built by a criminal who ate a cyanide pill during his trial.

These fantastically named natural pools look like something out of a Scottish myth.

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