Collapsing castle on the Hudson river was once the storage site of military surplus business.

A crumbling hospital from the 1850s on Roosevelt Island.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

World's first "penitentiary," meant to be humane, drove men insane.

Abandoned Coast Artillery fort now serves as graffiti canvas and sightseeing vantage point.

The once-abandoned 140-year-old hotel used in the movie "In Dreams."

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

A formerly abandoned mental institute, now back in business.

The feral felines of Roosevelt Island have a small army of allies and an abandoned hospital all to themselves.

Run by a eugenics advocate, this aging institution conducted secret radiation experiments sponsored by Quaker Oats.

Decades after testing the polio vaccine on unwitting patients, this historic mental hospital sits in ruin.

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

Site of a famous 19th-century transcendentalist utopian community, now abandoned.

This abandoned psychiatric hospital once housed more than 4,000 patients in the middle of a quaint New England town.

The remains of a deserted 1800s farming community can be found in Little River State Park.

An iconic steel and chrome diner from the 1940s left empty for nearly 20 years is in danger of being demolished.

In the woods of New Jersey lie the ruins of a munitions village abandoned after World War I and the remnants of a 1920s wooden racetrack.

A recently abandoned psych ward at the end of Sanatorium Road.

An abandoned Depression-era zoo hidden just off the highway.

Forgotten under the construction of a new urban roadway is a small, abandoned part of town.

The ruins of an abandoned 18th-century town that is slowly being reclaimed by the forest.

Hundreds of numbered stakes hidden in the woods mark the graves of the lost souls of a nearby asylum.

This dam in the woods, built by Henry Ford with only manpower and oxen, holds no water and serves no purpose.

Ruins of a historic medical facility sits eerily by the water.