Another of California's unused Cold War missile defense complexes has become a graffiti gallery.

Forgotten and then destroyed by fire, this was once one of the largest saltwater swimming pools in the world.

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

The old Niles Canyon Aqueduct in the San Francisco Bay Area is a bemusing and secret trail through nature for wayward travelers.

Amazing meticulous gardens of personal wood carvings, Hydrangea, Canna, and many other flowers.

A promotional sun clock on the site of San Francisco's great raceway.

Once the largest windmill outside of Holland, with enormous 114 foot sails.

The key to turning shifting dunes into the green oasis of Golden Gate Park.

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

The one-time watch house for incoming ships at the Golden Gate now stands abandoned and hidden in trees.

Big gun installations, built over a massive cemetery, now abandoned & hidden in trees.

The remains of a ruined mansion memorialize the 1906 earthquake.

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

Relics of the 1894 Midwinter Exposition continue to delight visitors today.

An elaborate gift from Claus Spreckels is now a piece of San Francisco history.

A winding path built in secret on the edge of the continent.

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

San Francisco’s condensed garden of incredible plant growth.

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

A favorite haunt of dinosaur loving children and hallucinogen loving hippies alike.

Adolph Sutro's little-known, geographically inaccurate, deprecated monument.

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

This private residence was the template for one of the most beloved television homes of all time.

This abandoned boat was left in place thanks to its rotting beauty.