These beautiful ruins deep in the Pennsylvania woods are thought to have been a ski lodge or a speakeasy, but no one really knows.

The dairy farm in upstate New York where nearly half a million people gathered for three days of peace and music in 1969.

The haunting, dilapidated remains of a former poorhouse on Staten Island's Greenbelt.

Created by four famous men (Henry Hobson Richardson, Frederick Law Olmsted, Calvert Vaux and Thomas Story Kirkbride), the beautifully designed Buffalo State Asylum was resurrected as a hotel and art center...but still boasts a ghost story or two!

This former abandoned hospital, a complex of stunning 19th century buildings, once housed 2,000 psychiatric patients.

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

Read between the lines of the subway map to find the hidden abandoned Civil War fort.

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

The abandoned husk of a mental institution that failed to save a Jazz Age icon still sits nearly unchanged.

An abandoned asylum once on the cutting edge of lobotomies may be reborn as a Christian college.

A once crucial portion of the Long Island railroad still lays abandoned, waiting to be turned into an urban park.

Once America's longest-manned military fort, now an abandoned hulk.

This once-grand marvel of engineering is now 41 miles of scenic hiking trail.

Six peaceful acres in a residential neighborhood dedicated to art and peace.

A long abandoned hospital building on the outskirts of NYC.

The decaying ruins of Wales' first asylum for the mentally ill.