This dormant volcanic crater has been converted from a roiling pit of magma to a pleasant hiking spot.

A Roman-inspired temple once controlled half of San Francisco's waters.

The headquarters of a secretive order is also a beautifully-designed park.

California's own majestic geyser is powered by a subterranean volcano.

Once the gateway to the utopian dream-village of a Civil War embalmer.

A tribute to the life and work of the beloved "Peanuts" cartoonist.

Life in this isolated, hilltop lighthouse was lonely, but it sure was lovely.

A giant donut stands as a popular symbol of Los Angeles iconography.

Built by the inventor of the radio, this abandoned hotel has housed early radio employees, military men, and a dangerous cult.

Abandoned Air Force base that has fallen into disrepair.

The mysterious round rocks of Schooner Gulch.

Commonly referred to as the most photographed Victorian home in the United States.

Dive bar built out of the remains of a whaling ship.

The rusting remains of the largest assembled WWII fleet on the West Coast.

A world-class observatory in the California desert.

An extensive collection of ancient Egyptian artifacts and mummies.

This massive redwood tree has a hole in the base big enough to drive through.

The haunting ruins of Jack London's dream house.

One of the most scenic stretches of road in America winds between some of the country's oldest trees.

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

Costumed elves and mountain bikers co-exist peacefully at this abandoned Christmas-themed adventure park.

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

A hotel and restaurant serving as the mecca of kitsch.

Towering basalt columns, a creation of fire and ice.