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

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.

An essential stop before plundering, BYO Cutlass.

The oldest burial ground in the city, final resting place of city founders, Ohlone natives and murderers alike.

The restored and active Victorian-era final resting place of San Francisco.

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

Home to one of the world’s largest collections of model yachts.

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

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

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

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

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

The remains of a ruined mansion memorialize the 1906 earthquake.

Olfactory delights in San Francisco's Botanical Gardens.

Golden Gate Park's historic collection of plants.

The remains of a 12th-century chapter house in Golden Gate Park.

California's most comprehensive horticultural library.

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

A shop full of natural curiosities, carnivorous plants, and costumed taxidermied mice.

A French chateau, failed utopian community, odd museum, and Stonehenge replica in rural Washington State.

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

Standing in a state of "arrested decay," this ghost town allows for a detailed peek into Gold Rush life in an unusually harsh climate.

A collision of human error and natural geothermal pressure created this rainbow-colored geologic wonder.