Gorgeous cave resemble a winter wonderland.

This unusual lava tube spouts seawater during high surf.

Rainbow-hued in the summer and crystalline in the winter, this salty lake has inspired battles, temples, and plenty of awe.

A swing to dangle you off the very edge.

A turquoise lake within a volcanic crater.

On the Oregon coast there is a natural hole that seems to be draining the sea.

This huge pile of volcanic boulders hides a stunning network of secret grottoes.

The deepest lake in the United States, and once the site of epic destruction that lives on in legends.

This limestone cave offers an incredible view of the Río Grande de Arecibo valley.

The highest dunes in California are the most likely place in the area to hear the Singing Sands.

A graceful natural rock formation stands astride the point where the Gulf of California meets the Pacific Ocean.

Millions of glowing microscopic organisms light up the waters of this luminous lagoon.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

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

Seemingly grown on some other world, these New Mexico rock formations look like a disused science fiction set.

This naturally-sourced hot spring is now home to a clothing-optional resort.

The only swimming pool listed on the National Register of Historic Places is emptied and refilled each day with naturally filtered water.

A stunning, two-tiered waterfall made famous by poets, artists and the legend of a ghost dog.

This pebble beach is so beautiful that taking its rocks is against the law.

Enormous lake at the bottom of a unique cave system.

This natural wonder drops 16 stories straight down through rare flora and streaming waterfalls.

Labor provided by Great Depression-era programs restored these 25,000 acres in Tennessee.

Two monstrous faces loom over a village in Czechia.

A fiery crater has been burning in the Karakum Desert since 1971.