Visitors dip into a variety of pools of what was once ice.

Abandoned castle was once a grand example of Russian privilege, built exclusively to win a frivolous bet between noblemen.

This whimsical winery by Antoni Gaudí looks ripped from the pages of a fairytale.

An isolated village literally built into the crevices and rock formations of a mountain.

Amazing and mysterious Neolithic settlement on Scotland's Orkney Islands.

An alchemist's "magic door" stands in the middle of a Roman park.

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

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

This abandoned radar station from the Cold War era now only broadcasts a seriously ominous air of isolation.

The oldest surviving bridge in New York City, which reopened to pedestrians in 2015.

Civil War-era Fort designed to withstand invasion and attack, with tricky traps called "murder holes."

Last church of this militaristic WWII style.

The real life Hobbiton, this sheep farm has been forever transformed since being built for The Hobbit film series.

A scenic fort on the harbor protected Philadelphia from an attack that never came.

Jail from the 19th century that was built by inmates.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

One of the oldest reform schools in the United States, home to wayward boys such as Merle Haggard, now abandoned.

Former prison camp dedicated to the victims of political repression.

Extensive private collection of authentic Medieval devices used for human torture and execution.

Prison made famous by The Shawshank Redemption has been out of commission since 1990.

A series of five defunct panopticon prisons in Cuba.

World's largest collection of serial killer artwork and other macabre exhibits.

Medieval torture techniques with a modern conscience.

A 200-year-old prison that now houses a peculiar crime museum.