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

The graffiti-covered remnants of a former triangulation station are balanced precariously on this California peak.

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

An abandoned meat mecca now serves as an excellent locale for urban exploration.

A peculiar mansion built by the troubled heir to the Winchester Rifle Company fortune.

Recovered from the brink of extinction, at home in the Financial District.

Golden Gate Park's historic collection of plants.

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

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.

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

Staircase winds down the side of Telegraph Hill through gardens, wild parrots flying overhead.

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