Amid the bustle and noise of the Financial District hides a secluded garden oasis above the city streets.

A crumbling hospital from the 1850s on Roosevelt Island.

Russian history in San Francisco.

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

Since 1973, this block has been home to the most concentrated collection of murals in San Francisco.

The miraculous hydrant that saved the Mission District in 1906.

Tenacious mummies survived dental problems, eternal entombment, and more than their fair share of devastating fires.

This partially buried wreck is one of the most complete of its kind but is only revealed when the sea allows.

This turn of the century masterpiece has a mysterious goaty interloper.

A Barbary Coast watering hole built into a Gold Rush shipwreck.

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.

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

The remains of a ruined mansion memorialize the 1906 earthquake.

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

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

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.

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

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

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

A psychedelic labyrinth on the San Francisco bay.

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

The World's First 24 Hour Coin-Operated Art Gallery!! Plastic, Styrofoam, and Elvis--If you can't get rid of it, you might as well worship it!!

Beyond being incredibly fun, not much can be said about the Hole with certitude.