Oregon's unexpected high desert, displaying layers of time in a colorful show.

Bridges, terraces, and replicas of historic structures all built of rock and petrified wood by one man.

This massive mushroom has spent centuries eating its way across a huge swath of Oregon.

The only Native American museum along the Oregon Trail, run by the peoples who have lived on the land for generations.

An extraordinary mixture of natural beauty and man-made phenomena.

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

The first declared National Monument in the United States.

The only road through the heart of Glacier National Park.

A tiny red pebble marks what may be the quietest outdoor spot in the United States.

Shoreline strewn with the remains of ghostly fallen trees.

Largest cave system in Africa.

The library of every book lover's dreams.

This domed temple was built in a hidden cave mouth as a refuge for sinners seeking absolution.

Discovered by cows, these upstate New York show caves are presented with a healthy dose of psychedelic folk art.

Sail through this subterranean show cave that is home to a legend that would go on to name nearly everything around it.

These sub-farmland caves are home to a majestic stalactite known as the "Crystal King."

This controversial Irish show cave is home to a massive formation known as the Great Stalactite.

This haunting stone chasm is a hotbed of mossy rock and English legend.

Remote, volcanic island that Darwin, Hooker, and the Royal Navy shaped into a thriving, artificial ecosystem.

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

A lake with hundreds of ancient skeletons surrounding it. The surprise is what killed them.

This trio of Dominican cave lakes comprise a colorful biosphere of natural life.

This Sumatran root bridge took almost 30 years to knit itself together.

One of the Eight Wonders of Kansas and the first official National Natural Monument these stark formations look like nature's Stonehenge.