A surreal landscape where fanged rocks rise from the ground and the ocean feels like a great mystery.

This 40-room dwelling tucked within a cliff was built by the basin's prehistoric residents.

A partial tunnel blasted into a steep ridge is all that remains of a failed railway across Arizona.

An improbable waterfall springs from an orange-white cliff face, tumbling into the headwaters of the Virgin River above Zion National Park.

Local lore holds that Butch Cassidy took an escape route through Red Canyon's sandstone hoodoos after an attempted murder.

Despite a legend that says this highest peak in Oregon was climbed in high heels scores of people have died on its slopes.

The longest continuous lava tube in Oregon.

This large maar crater in Oregon is the bigger brother to Hole in the Ground.

This natural marble cave is one of only five national monuments in Oregon.

A cave's rare beauty held a cavernous secret hidden underground.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

The marker offers a rare chance to be in four U.S. states at once, though there's some controversy over its geographic accuracy.

A striking, menacing sandstone peak towering above a landscape that's equal parts Mordor and the Moon.

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

Rippling sand dunes frozen in the Arizona rock.