This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

"May prick nor purse ne'er fail you."

There's a labyrinth of manmade tunnels stretching for over an acre beneath Bristol.

A bronze tribute to the wildly popular video game from the '90s.

This enormous secondhand bookstore inside a Victorian train station sparked the "Keep Calm and Carry On" craze.

These mysterious religious carvings were once thought to be thousands of years old but are actually the work of modern eccentric.

Where the sleeping monsters of Scotland's oil industry are left to rust.

The only fixed chain and post trail in Scotland snakes its way along the base of a towering seaside cliff.

One man spent 10 years building a spectacular section of road because no one else would.

A remarkably well preserved tower dating all the way back to the Iron Age.

A pub that is literally in the middle of nowhere, but continues to do business.

London's largest outsider art museum.

The last inhabitants of one of the U.K.'s most remote islands were evacuated in 1930.

Accessible only at low tide, the deserted island is dotted with World War II ruins.

This series of Scottish caves has no clear purpose other than baffling historians.

The atmospheric road was never meant to be so creepy.

The once forbidden "secret cabinet" of erotic art from excavations of Pompeii and Herculaneum.

The burial place of an obscure North African saint was turned into a macabre body preservation factory for the 17th-century Neapolitan elite.

Dug as a secret royal escape route, the tunnel became a wartime bomb shelter and dumping ground for vintage cars.

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.

This floating garden in the sky is straight out of a fairy tale, but the real thing is nothing short of magical.