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

Found art has transformed this Pittsburgh neighborhood into a psychedelic dream.

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

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

Hundreds of glow-in-the-dark objects light up a museum in a historic zinc mine.

A hands-on traveling collection of the innovative devices of yesteryear.

Along the Palisades skyline are the ruins of a large mansion built in 1911 and demolished in the 1930s.

One of the last Jazz Age "Wonder Theaters" in New York City.

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

These World War I shooting range tunnels are now haunted halls of underground graffiti accessed through the roots of a tree.

This abandoned subway station can still be seen on regular commuter trips.

Buildings that dynamite couldn't bring down were abandoned because of bathroom issues.

The remains of a failed subway in upstate New York is now an underground graffiti bunker.

A tunnel once abandoned now thrives with graffiti art as an off-limits makeshift gallery.

A formerly abandoned mental institute, now back in business.

Beneath the mossy overgrowth covering this once-sprawling campus lies decades of history and the secrets that come with it.

Collection of trolley cars in the woods represent one man's attempt to preserve transportation history.

Where America's first doomsday cult awaited the end of the world.

A long abandoned hospital building on the outskirts of NYC.

Prove you deserve to be fed by Kenny Shopsin.

An abandoned stretch of highway, deteriorating next to the operational one.

Abandoned 19th century homes once occupied by naval officers, soon to be demolished.

Abandoned power station once home to a squatter community, now being developed into an arts center.

A museum devoted to bringing to light forgotten or neglected histories through exhibitions, education and public programming.