The last occupied troglodyte dwellings in England weren't abandoned until the 1960s.

A former reservoir that was only recently discovered after more than 60 years of disuse.

A once-booming Mississippi River town with a history of racial violence is now eerie and mostly abandoned.

This lab's maddening silence is good for business but bad for sanity.

The "3rd largest" city in California is an empty mirage of suburbia in the middle of nowhere.

A huge musical instrument played by the ocean.

The colorful soil of Iran’s "Rainbow Island" attracts artists and nature lovers.

This ancient settlement contains some of the largest earthen mounds in North America.

These mystical miniature houses bring a touch of magic to the New Jersey woods.

An 18th-century Catholic church converted into an eccentric temple of music and bacchanalia.

The first tunnel to be dug beneath a river, repurposed as an art and museum space.

A 19th-century subterranean reservoir repurposed as a contemporary art cave.

Designed as a labyrinth, this subterranean prison was crafted without bars or doors.

This iconic L.A. bookshop is housed in an abandoned bank—both symbolic and chic.

Denmark’s never-ending bridge.

During prohibition, corrupt city officials ran drinking dens under the streets of Downtown Los Angeles.

For six months of the year, three giant mirrors direct a pool of sunshine onto this otherwise occluded town.

A peculiar mansion built by the troubled heir to the Winchester Rifle Company fortune.

You can only access this hermitage by crawling under a ledge suspended above an overhang.

A lonely beacon, precariously perched atop a remote sliver of rock.

Home to the world's oldest wooden building.

Hellam Township is reputed to feature seven remote gates, which when passed through in the right order, open an entrance to hell.

Veryovkina Cave is more than 1.3 miles deep—the deepest known in the world.

Once thought to be the oldest living tree in the world, Methuselah was germinated before the Egyptian pyramids were built.