A ghost town at the airport is now a refuge for blue butterflies.

Visible below the waves are memorials to the city's Gold Rush dead.

Eons old volcanic activity created one of the most stunning rock formations in the United States.

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

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

This strange seaside tower got its name from a wealthy eccentric who would hide coins among its stones.

A pair of slides and a tree-lined stair corridor have been an urban oasis for nearly 40 years.

Towering basalt columns, a creation of fire and ice.

Its buzzing collection honors vibrator history.

Carnivorous plants, medieval aphrodisiacs, and the largest original wood structure glass conservatory in the western hemisphere.

The only theatre in the world constructed specifically for sound movement.

A tiny theater hidden in an alley plays a constant stream of short silent films for anyone willing to peer through the peephole.

One man's homage to the sun continues to grow like a glass fractal.

The abandoned zoo enclosures offer a perfect place to experience the other side of the bars.

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

Bring your own cardboard to the slippery slopes of concrete hidden in a neighborhood park.

A psychedelic labyrinth on the San Francisco bay.

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

A huge musical instrument played by the ocean.

The second largest waterfall by volume in the U.S., Willamette Falls is outdone only by Niagara in the amount of water that is pushed northward.

Marta Becket's hand-painted theater in the desert.

Its dark depths conceal millions of rare, delicate crystal formations.

A popular tourist cave with a dark past.

Under the right circumstances, this waterfall in Yosemite briefly turns a luminescent fiery orange.