A sprawling cave network created by a lone lava tube.

Atop an active stratovolcano, two lakes separated by a narrow strip of land.

The longest continuous lava tube in Oregon.

A rugged lava field dotted with molds of the ancient pines that were growing when the volcano erupted.

One of the last free public hot springs is decorated with hippie art.

An underground mansion with fruit-bearing trees and grapes growing beneath the surface of central California.

This rock formation named for its unique shape is one of many that call the Alabama Hills home.

Once thought to be the oldest living tree in the world, Methuselah was germinated before the Egyptian pyramids were built.

A mountain range on an active U.S. Navy base hides thousands of mysterious prehistoric rock carvings.

Abandoned hotel with adjacent lake and golf course.

The "3rd largest" city in California is an empty mirage of suburbia in the middle of nowhere.

Etched into a dry lake bed, this massive directional indicator is accurate without magnets.

Everything you always wanted to know about borates is here.

Odd outsider art installations surround a Gold Rush-era ghost town.

The most magnificent bottle house in a town strangely full of them.

A land of debatable treasure.

Aqueducts have dramatically changed this old lake, now home to tufa towers and its very own species of tiny brine shrimp.

California's oldest wind harp represents a historic piece of America's Danish history.

The first attack on the continental U.S. during WWII occurred off the coast of a quiet California golf course.

The ruins of the castle that chemicals built.

From Japan to Italy, this California park explores the world's cultures through their gardens.

Abandoned in 2009, this once popular resort destination now stands frozen in time.

Graffiti-covered ruins that were once part of a farm owned by a mental hospital.

"Looks so real, it's scary!"