From the sky, a kaleidoscope of color brightens the grey landscape of the San Francisco Bay.

San Francisco Bay's ghost town.

From the Difference Engine to the Cray-1, all under one roof.

A statue commemorate Tommie Smith and John Carlos's brave protest at the 1968 Olympics, a watershed moment for civil rights.

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

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

The yawning maw of this pagan visage is said to bite off the hands of liars.

The final resting place of the poets Shelley and Keats.

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

Rome's semi-secret peephole vista is also a former Crusader stronghold.

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

An overlooked and unassuming engineering marvel.

A monument to the love people have for their pets.

Relics of the 1894 Midwinter Exposition continue to delight visitors today.

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

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

Home to the "Circus" trees created by Axel Erlandson.

Housed in a memorial lighthouse, this museum relays the history of surfing, beginning with the antics of royal Hawaiian teenagers.

This concrete ship has had four careers - World War I tanker, floating amusement park, fishing pier, and artificial reef.

A "gravitational anomaly" located in the redwood forests just outside of Santa Cruz, California.

A pair of pure white felines guard the entrance to a spot of California real estate established as an artist's haven.

One of the largest free-standing structures ever built, this dirigible hangar is now simply a giant skeleton.

This giant shopping mall still holds signs of its automotive past.

The largest permanent Monopoly board makes one of the longest games even bigger.