A burnt orange monolithic dome structure perched on a hillside near Interstate 280.

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

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

Spiral labyrinth hidden in the hills above Oakland, CA.

This odd California folly seems like it was almost designed to accumulate urban legends.

A former poultry store that looks like a giant duck and is one of the "seven wonders" of Long Island.

Collapsing castle on the Hudson river was once the storage site of military surplus business.

Whale bones, scrimshaw, and sperm oil make up just a part of this comprehensive collection of whaling history.

This limestone cave offers an incredible view of the Río Grande de Arecibo valley.

This imposing memorial contains the remains of Che Guevara — and 29 other guerrillas who died with him in Bolivia.

Once a favorite playground for the world's most illustrious guests, Hotel Nacional's secret weapons and bunkers reveal a more menacing side to its golden history.

A focal point of the Cuban government, this city square features one of the most iconic images in the country.

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

Concrete strongholds stand guard over the Golden Gate.

A man-made island in scenic San Francisco Bay.

Depicting scenes of everyday life - and specific individuals - in Great Depression era San Francisco.

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

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

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

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

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

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

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

Prone to disastrous fires, the city of San Francisco has the Guardian, a fireboat gifted by residents, to watch over them from the bay.