In a 345-million-year-old cave that's 200 feet underground, dinner awaits.

A gothic palace of endless stalagmites and pseudoscorpions waits within one of the world's most beautiful caves.

The longest continuous lava tube in Oregon.

Trails through lava-carved tube-caves display sparkling bacteria and a rich history.

A meditative space out of a fantasy story.

This temple, built by an eccentric religious leader before his death, sits guarded and in ruins.

In the middle of an extremely unforgiving and desolate high desert is the most secret military facility in the world.

Millions of years of oxidation make a drive down this winding Death Valley road surprisingly colorful.

One of the most unusual geological features, recognizable from a dozen hit movies.

Inky sludge oozes to the surface of this beach thanks to a rare natural tar seep.

Each winter this underground cave forms a dazzling ice palace.

A hard-to-reach oasis in a desolate corner of Death Valley National Park.

Sunset-colored dunes of volcanic ash make taking a poor photo impossible.

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

A grove of "candelabra redwoods" deep in California's Lost Coast.

Under the right circumstances, this waterfall in Yosemite briefly turns a luminescent fiery orange.

A raised boardwalk winds through a thicket of stunted, century-old trees no more than nine feet tall.

Its dark depths conceal millions of rare, delicate crystal formations.

More than 700 species live within this murky marvel of a swamp on California's coast.

This Big Sur waterfall drops 80 feet directly into the Pacific Ocean, and inspired the hillside house up top.

The old Niles Canyon Aqueduct in the San Francisco Bay Area is a bemusing and secret trail through nature for wayward travelers.

Forgotten and then destroyed by fire, this was once one of the largest saltwater swimming pools in the world.

A crumbling Beaux Arts monument to the Bay Area's age of rail.

This mysterious and creepy location instills a strong sense of foreboding in all visitors.