A humid oasis combines recreation with exploration in a unique underwater cavern.

A popular swimming hole that hides one of America's most deadly diving spots.

No one is quite sure of the origins of these idyllic natural hot springs at an abandoned mountain resort.

Clap your hands at the base of the pyramid, and the song of a sacred Mayan bird will echo through the air.

The ruins of an ancient island city built atop a coral reef in the South Pacific are spectacular and strange enough to have inspired H.P. Lovecraft.

A ruined mansion hidden in the woods of the Hudson Valley, home of a tragically doomed romance.

Reforestation in action is the main attraction in this abandoned quarry.

This abandoned factory on the Hudson River once churned out a million bricks a week.

A 19th century hat factory still stands as a crumbling ruin in upstate New York.

Hear, smell, see, taste, and touch history at this immersive Civil War hospital.

A lone historical marker off the highway and scattered debris are all that remain of this Cold War-era missile site.

The famous abolitionist’s preserved estate is one of Washington's finest monuments to its great Black citizens.

Government testing at the asylum briefly explored using marijuana as a "truth serum" on Nazi prisoners of war.

The untimely death of a dignitary's daughter led to this fort being abandoned before it was ever finished.

L. Frank Baum wrote part of the "Wizard of Oz" series in this wooden Victorian beach resort.

A beautifully designed asylum was resurrected as a hotel and art center with a ghost story or two.

A former mental hospital founded in the 1930s by a eugenicist who advocated for the forced sterilization of patients.

One of the largest-ever mental hospitals now sits abandoned, surrounded by 25,000 unmarked graves.

Once a state-of-the-art tuberculosis treatment spa, these ruins are now ruled by paintball players.

Clusters of abandoned buildings hint at the facility's 144-year history with psychiatric health.

An abandoned asylum where patients have been forgotten but their possessions remain.

Considered one of the most haunted places in Europe, this 800-year-old castle was home to noble prisoners.

The first geometric self-supporting spiral stairs in Britain are a truly beautiful sight.

This collection of over 50 classic pinball machines awaits visitors to downtown Roanoke.