A hidden subterranean installation offers a view of the sky.

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

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

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

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

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

San Francisco's newly reopened hands-on science museum.

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

Get lost in this haunting fairytale art walk through a man-made eucalyptus grove.

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

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

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

The giant pair of sexy legs sticking out the window of this costume store have become its main draw.

A huge musical instrument played by the ocean.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

Nursery with extensive collection of flesh-eating plants operated by the author of "The Savage Garden."

Monumental sculptures of Patrick Amiot, constructed from debris, detritus, and determination.

California's own medieval Italian castle, authentic down to the 300-year-old iron maiden in the dungeon.

A tribute to the life and work of the beloved "Peanuts" cartoonist.

This stretch of beach along California's central coast is a busy highway for the largest seal in the northern hemisphere.

The unbelievably opulent home built for an infamous newspaperman.

A massive volcanic plug is now a protected area that hosts a number of bird species.

There is no trying to fall in love with this Star Wars fountain, you just do or do not.

This remarkably simple jail went over a century without an escape.