A psychedelic labyrinth on the San Francisco bay.

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

A huge musical instrument played by the ocean.

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

A strange house built only at night, with rumored mystic inspiration.

An extensive collection of ancient Egyptian artifacts and mummies.

San Francisco Bay's ghost town.

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

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

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

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

A shop full of natural curiosities, carnivorous plants, and costumed taxidermied mice.

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

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

A tiny theater hidden in an alley plays a constant stream of short silent films for anyone willing to peer through the peephole.

Enter the world under the hill at this ancient UK burial chamber.

This Scottish burial tomb once held hundreds of ancient eagle bones.

Thanks to both terrific preservation and historic vandalism this ancient site is known as the "Heart of Neolithic Orkney."

This tiny island featuring 9th-century Viking ruins is only accessible at low tide.

A red sandstone freestanding monolith rises out of the sea in northern Scotland.

Possibly the oldest of Britain's ancient henges is also one of its most stark.

The true age of this ancient stone circle is unknown, but its stunning vista isn't in question.

An abandoned tuberculosis hospital said to be haunted by the patients who died within its walls.

An ancient tomb that still stands in Portugal.