Although it appears ancient and mysterious, the quirky folly was actually built 200 years ago by an eccentric estate owner.

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

Huge concrete structures designed as an early warning system for Britain to detect enemy aircraft.

Monty Python fans will recognize this abandoned mine as the Cave of the Killer Rabbit of Caerbannog.

The remains of an ancient Roman teenager are memorialized at the base of a modern London landmark.

A open air theatre built on a cliff by an eccentric British woman.

This beautiful "lagoon" is actually a toxic soup filled with cars, carcasses, and trash. When warnings couldn't stop people from going for a dip, the town dyed it black.

London's largest outsider art museum.

Old-fashioned knowledge and modern engineering create the world's only rotating boatlift.

The oldest inn in England served brew to the crusaders.

This abandoned asylum in Wales might look haunted, but it's still beautiful.

The heads of two giant mythological water horses honor Scotland's horselord past.

Rebuilt remains of a temple to Roman god Mithras.

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