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

Golden Gate Park's historic collection of plants.

An overlooked and unassuming engineering marvel.

The stones that traveled from Spain to eventually become a holy place for San Francisco's nature worshippers.

A hidden subterranean installation offers a view of the sky.

Thirteen trees representing the original thirteen colonies were planted with soil from historic Revolutionary battlefields.

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.

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.

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

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