San Franciscans leave gifts and messages for the magical beings that live behind the tiny, mysterious door installed on a tree in Golden Gate Park.

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

The remains of a ruined mansion memorialize the 1906 earthquake.

A modern mechanical planetary system, part of a 10,000 year clock.

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

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

The tea room that pushed the boundaries of adorable straight into...we can't find the words.

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

An essential stop before plundering, BYO Cutlass.

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

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

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

Nestled in the heart of San Francisco’s bustling Financial District stands a unique homage to the Mayan and Beaux Arts.

Alleyway plaque commemorating the death of a fictional character in The Maltese Falcon, not far from the author's home.

Not merely a museum – but a whirring powerhouse that offers a subterranean peek into the heart and soul of cable car operations.

The first AIDS memorial chapel in San Francisco and one of only a few in the U.S.

A walk-in working camera obscura produces 360-degree live images of the San Francisco coast.

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

Its buzzing collection honors vibrator history.

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

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

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

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

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