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

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

Its buzzing collection honors vibrator history.

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

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

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.

A huge musical instrument played by the ocean.

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

A whimsical antique shop with a strong air of mystery, filled with items from ages, and what feels like worlds, past.

San Francisco's oldest surviving monument and meeting place for 1906 survivors.

Floating man-made island and upscale restaurant.

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

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

Gold Rush-era tombstones line the park's paths.

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

Half of a house.

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

A library and museum dedicated to typography.

The oldest lawn bowling club in the United States.

A classic advertising icon immortalized in regal bronze.

Depicting scenes of everyday life - and specific individuals - in Great Depression era San Francisco.

San Francisco's first World's Fair, dedicated to the wonders of California.

These WWII-era murals were initially booed as a libelous portrayal of the American dream but have survived multiple attempts to have them destroyed.