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

The wooden octagon in which Huckleberry Finn and A Connecticut Yankee were born can still be visited in upstate New York.

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

Yale University's home for rare works, including the mysterious Voynich Manuscript.

The life of one of FDR's possible mistresses is preserved in her palatial Hudson Valley mansion.

This tiny New Jersey village has lived many lives but seems determined to remain a ghost town.

This throwback amusement park is home to rides and unique storybook figures from the past.

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

Golden and naked, the figure that was once the highest point in New York is all that remains of the second Madison Square Garden.

This decrepit abandoned building is made all the more eerie by its dark history.

A former seaside jewel built for the everyman is now simply a neglected art deco fortress.

This abandoned seaside fortress is now simply an imposing ruin being taken back by nature.

Holding multiple historical boats and an entire 19th century village, this New England attraction is the largest maritime museum in the world.

These mouldering mansion ruins remember a time when the Catskills were nothing but luxury.

Public outcry led to this bridge's unique character which celebrates a giant frog battle and also sewing.

An Irish Memorial commemorating those who perished due to potato blight.

Made of bronze and wearing a blue gown, this lady sat in the same location in the Yantic Cemetery for more than 119 years.

This peaceful Massachusetts graveyard was one of the first "garden-style" cemeteries in America.

The US Navy's only submarine museum is also home to the world's first nuclear submarine.

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

A museum designed by and dedicated to P.T. Barnum in the town where he is buried.

This small-town pizzeria won the Hollywood lottery.

A former copper mine which became a truly unsuccessful prison.

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