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

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

San Francisco's urban bison herd has persisted in the face of extinction, development, and disease.

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

A nondescript building that's been functioning as a speakeasy for nearly a century and a half.

An essential stop before plundering, BYO Cutlass.

The randomness of this wall of lava lamps helps encrypt up to 10 percent of the internet.

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

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

A collection of 20th-century automata, penny arcade games, and musical contraptions.

Staircase winds down the side of Telegraph Hill through gardens, wild parrots flying overhead.

The seawater playground of gilded-era San Francisco burned to the ground in 1966.

Its buzzing collection honors vibrator history.

Tiki luxury on Nob Hill.

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

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

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

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

A huge musical instrument played by the ocean.

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

A museum dedicated to celebrating the humble wingnut.

These subterranean storage areas hold emergency water reserves.

A replica of the decorated wooden pillars Viking sailors threw overboard when finding new places to establish a settlement.

This antique shop specializes in the history of print and design.