A 140-year-old castle with underground caves hidden in San Francisco.

The legendary building that needed ghostly approval before being built.

High on a hill overlooking Los Angeles lives a world famous, high power conical Tesla Coil.

A psychedelic labyrinth on the San Francisco bay.

An artsy hidden staircase leads to breathtaking views of San Francisco.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

World's largest collection of serial killer artwork and other macabre exhibits.

Remants of foundations, streets, and streetcar tracks inhabit the cliffs where a landslide occurred in 1929.

A huge musical instrument played by the ocean.

A peculiar mansion built by the troubled heir to the Winchester Rifle Company fortune.

California's longest-running tourist attraction is a stump.

A popular tourist cave with a dark past.

Hidden beneath a lake for decades, this brutalist mine has now emerged from beneath the receding waters.

A cozy bookstore is tucked within an old gold mine shaft beneath the cafe and ice cream shop.

Where the writer penned his famous story about a jumping frog.

This museum boasts the ninth-largest collection of insects in North America.

A huge collection of rocks, gems, and crystals.

This corn maze so big you may want to pack a lunch, and possibly a flaregun.

This 19th century train workshop is a treasure trove of railroad history.

A fascinating and comprehensive look at the evolution of medical practice in the Sacramento Valley since the mid-1800s.

At this 1940s-era neighborhood favorite, you can still drink a cherry phosphate.

Founded in 1873 to support the needs of the gold mines flourishing nearby, this is the last water-powered foundry in the United States.

Now a secluded county park, this site was once a "health tourism" destination for wealthy Oregonians.