The world's first permanently occupied mountain-top observatory continues to report on the stars.

Educational foundation that teaches the powers of fourth dimensional physical properties.

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

The only visible piece of San Francisco's most famous shipwreck.

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

A free library to stumble across, one of many placed worldwide if you know where to look.

The world's largest wooden trestle stretches across this desert canyon in Anza-Borrego Desert State Park.

California's oldest wind harp represents a historic piece of America's Danish history.

This large collection of tiny things revels in the art of fine machinery well made.

Secret US military film studio in the Hollywood Hills.

In the middle of the desert, miles from any human life, sat an anomalous pay phone that still magically answers your calls.

The Los Angeles flood disaster that took 400 lives and ended the career of William Mulholland.

This historic tower in the California desert promises visitors a "vortex of good vibes".

Suburban observatory was personal lab of the father of modern astrophysics.

A Biblically-based Natural History Museum.

This Oakland fairytale kingdom, fiercely devoted to childlike whimsy, was an early inspiration for Disneyland.

This glamorous old building is said to have inspired the Tower of Terror.

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

Nationwide network of co-ownership underground catastrophe shelters.

A tree grown from astronaut seeds which were exposed to cosmic rays.

The miraculous hydrant that saved the Mission District in 1906.

No matter what it might seem like on film, most scenes filmed on a plane are filmed at this LA studio.

The graffiti-covered remnants of a former triangulation station are balanced precariously on this California peak.

Radioactivity still cause for concern at this urban explorer's paradise.