A 19th-century cabin built into a hollowed-out Sequoia tree.

Four hundred granite steps were built into this massive rock by the National Park Service.

Quite simply the largest tree in the world (by volume).

The oldest continuously operating church in California.

One poet's handmade, anachronistic home.

An abandoned boat that's been stranded mysteriously for decades.

Once America’s most beautiful army base, this abandoned military fort on the coast of Monterey Bay has been left to the elements.

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

This structure among the trees was the result of divine inspiration.

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

The longest burning light bulb in the world.

Location of the most powerful laser in the world, and the potential birthplace of tiny stars.

This hidden amusement park is a magical escape for kids and kids-at-heart.

A bizarre house filled with an astounding array of collections.

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

Subterranean house made out of a grain silo, located in the Santa Cruz Mountains.

The largest self-built castle in the U.S., six decades in the making.

A man's home is his castle.

A house built from trash known as the poor man's Hearst Castle.

"I did this all while you were watching TV."

A private home built to resemble the shape of a microscopic creature.

An eccentric folk art landmark made out of discarded bottles by an inspired "grandma."

An eccentric home stands out in an otherwise average neighborhood with mosaics, mini topiaries, and kinetic sculpture.

California's own medieval Italian castle, authentic down to the 300-year-old iron maiden in the dungeon.