It took years to decode its mysterious messages.

It is locally loved and ridiculed for literally looking like poop.

Eight huge lanterns lining a city street can change color on command.

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

This concrete tangle of square pipes has stood as a proud thorn in the city's side since the '70s.

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

The remains of a ruined mansion memorialize the 1906 earthquake.

In this century-old literary safehouse, print is alive and well.

A 300-ship graveyard, with a few still visible at low tide.

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

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

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

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

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

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

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

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

A museum befitting the city responsible for supplying the majority of the world's LSD.

Its buzzing collection honors vibrator history.

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

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

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

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

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