A piece of outsider public art accompanied by a strange urban legend.

The show's fictional Korean medical camp was created in the Santa Monica hills.

A mapping error in the 19th century made loggers think this section of the forest was underwater.

A retrofuturistic art installation in the Pittsburgh Airport.

This large midwestern cavern features impressive rock formations and an underground waterfall.

Rotting dome home spotted near Chapel Hill, North Carolina.

An oversized metal construction of Billy Tripp's moods going through life.

Railroad came. People came. Railroad left. Town died.

This road in the Great Smoky Mountains was supposed to assuage a displaced community, but ended up a $52 million dead end.

Minnesota's oldest and deepest mine is now an underground physics laboratory.

The world's first underground farm is in a World War II bomb shelter beneath the streets of London.

"Purveyors of traditional sweets and vintage treats."

A historic house left in "dramatic still life."

The popularity of Sherlock Holmes led to the creation of his fictional address, turning the orderly London street numbers askew.

A subterranean ice warehouse that has lain hidden beneath central London for over a century is now open to the public.

In this cobwebbed old operating theater, you can practically hear the screams of the unanesthetized patients.

The curios of pharmacist and collector Henry Wellcome.

The signs of a long buried road can still be found hidden beneath a London sewer grate.

Art Deco and “Wrenaissance” mash-up, this recently restored royal residence has been home to kings and comes with secret monkey passages included.

This hidden rooftop garden in downtown London offers a quiet respite from a bustling city.

The remains of one of America's first radiation testing grounds still rest ominously in a Georgia forest.