Barely visible foundations remain where Stow Lake’s “observatory” once welcomed visitors.

The remains of a ruined mansion memorialize the 1906 earthquake.

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

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.

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.

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

A modern frieze of ancient Grecian mythological figures playing a national pastime.

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

A classic advertising icon immortalized in regal bronze.

The original place where water met land in the City by the Bay is outlined in brass.

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

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

A trash dump made beautiful by nature's power.

The only standing town in the United States that early Chinese Americans built for themselves.

A four paneled, brightly multicolored mosaic adorns the side of this popular grocery store.

Built in 1906, this unique building was the first Hindu temple in the United States.

Once the fastest ship from San Francisco to Tahiti, the Galilee now lays in pieces in three different cities.

27-room home built with the fortune of a sugar magnate.

One of few lasting examples of the brief octagon craze that developed into folly.

A brooding mansion of clinker brick stands out among the Victorian houses of Pacific Heights.

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

Its buzzing collection honors vibrator history.