A monumental cross hides in the trees in Golden Gate Park.

Floating man-made island and upscale restaurant.

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

An elaborate gift from Claus Spreckels is now a piece of San Francisco history.

Golden Gate Park's historic collection of plants.

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

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

Big gun installations, built over a massive cemetery, now abandoned & hidden in trees.

Guns that have been defending San Francisco since 1904.

The key to turning shifting dunes into the green oasis of Golden Gate Park.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

Once the largest windmill outside of Holland, with enormous 114 foot sails.

The century-old bell and clock tower at UC Berkeley is the third-tallest in the world, and has fossils.

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

A huge musical instrument played by the ocean.

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 New England-style lighthouse along California's beautiful Highway 1 gets a re-do.

Concrete strongholds stand guard over the Golden Gate.

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

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

The one-time watch house for incoming ships at the Golden Gate now stands abandoned and hidden in trees.

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