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

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

A Barbary Coast watering hole built into a Gold Rush shipwreck.

A treasure trove of artifacts, books, and artwork from the "golden age" of exploration.

Nondescript elevator doors open to reveal a stunning, surreal world.

Unlock the secrets of the conjuring arts.

This stunning Connecticut mansion is actually just a one-room-deep hoax.

A famed data visualizer's personal sculpture garden is a landscape of modern and megalithic wonders.

A former copper mine which became a truly unsuccessful prison.

An Escher-inspired library dedicated to the wonders of the human mind, yet closed to the public.

The one-stop shop for all of your superhero (or evil arch-nemesis) needs.

A museum devoted to bringing to light forgotten or neglected histories through exhibitions, education and public programming.

A bizarre house filled with an astounding array of collections.

Home of Philip Johnson, one of the 20th century's most influential architects.