Shoreline strewn with the remains of ghostly fallen trees.

Where monkeys run wild and the humans are caged.

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

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

Moss and stone turn this waterfall into an otherworldly liquid veil.

One of the most scenic falls in Massachusetts has a history of death and grim legend.

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

The longest continuous lava tube in the continental U.S. offers 2.5 miles of dark explorations for the adventurous.

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

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

Submerged trees jut ghost-like out of an idyllic turquoise mountain lake.

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

Limestone caves with spectacular showcase chambers.

Enchanting cave with a river crashing through the roof.

A desert that rolls right up to the ocean, where it's so dry animals live off the fog.

Erosion and time have created a naturally-formed water park.

Stunning wetlands ablaze with pink lotus flowers.

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

A giant 400-acre preserve in North Florida for displaced wolves.

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

A glacier pocked with ice caves and surrounded by rainforests.

These Great Lakes sea caves accessible by boat in the summer turn into temples of ice reachable by foot in the winter.

This stream-carved gorge has inspired poets, hidden smugglers, and trained soldiers, all without losing its beauty.

Wondrous sandstone hoodoos where Native Americans collected clay for pottery, 9,000 years ago.