A psychedelic labyrinth on the San Francisco bay.

At the base of the Golden Gate Bridge, a small sign basically begs for a high-five.

Beneath the southern end of the Golden Gate Bridge is the “Gibraltar of the West Coast,” a fort built to protect the San Francisco Bay from naval attack.

Third time's a charm, or in this case, two testicles are.

Browse through a century of this principality's first popular export.

Liechtenstein's royal family calls this medieval alpine castle home.

Historic fortifications form the boundary of Vatican City, but it’s not entirely surrounded by walls.

The San Marino-Rimini railroad was short-lived but this tunnel once provided shelter for hundreds of refugees during World War II.

The stones of this formerly witch-obsessed castle were used to build a church.

Soaring over 6,000 feet in the Bavarian Alps, this beer garden was once Hitler's 50th birthday present.

The memory of the ancient unit of measurement of local builders.

The only visible piece of San Francisco's most famous shipwreck.

A vast city of the dead, where the deceased outnumber the living by more than a million.

The peaceful gravesite of a rugged wild west gunman echoes the touching story of his last days.

Visible below the waves are memorials to the city's Gold Rush dead.

Adolph Sutro's little-known, geographically inaccurate, deprecated monument.

Gold Rush-era tombstones line the park's paths.

A 300-ship graveyard, with a few still visible at low tide.

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

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

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

A modest reminder of treacherous waters at the Golden Gate.

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

A hidden gem, named after a San Franciscan icon, offers spectacular views of the Pacific Ocean.