One man's swirling six-acre monument of stone.

A once grand hotel is being retaken by the wilderness it once capitalized on.

The world's largest kaleidoscope, designed by a 1960s psychedelic artist.

Homemade rockets, dinosaurs, and robots make this New York small business much more than a furniture store.

What was once a trend-setting, phrase-coining icon of architectural splendor is now a rotting, forgotten hulk.

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

The Hudson River School comes alive at this palatial estate.

A stunning, two-tiered waterfall made famous by poets, artists and the legend of a ghost dog.

An abandoned 19th century quarry in the middle of the woods, remade by unnamed wanderers into a massive series of rock thrones.

An abandoned dollhouse factory.

Eccentric concrete mansion and museum designed and built by hand from the inside out.

This might just be the TARDIS of bookstores.

A unique sculpture park that specializes in the huge and bizarre.

This stone tower marks a lookout point over the historic Washington Crossing, and maybe some buried treasure.

The remnants of two World's Fairs are here, complete with a 12-story globe, a mini-Manhattan, and a UFO-shaped pavilion.

Lie in a hammock where George Washington stood.

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

The home of aviation trailblazers, in a remote corner of the big city.

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

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

The mass grave of a heroic Revolutionary War regiment sits below an empty lot near the Gowanus Canal.

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

Records of the dead describe the myriad odd ways people used to die.

A mass grave for victims of one of the city’s worst fires.