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

Astonishing collection of helmets, scientific instruments, and medical models.

An Escher-inspired library dedicated to the wonders of the human mind, yet closed to the public.

A world-class collection of mechanical musical instruments and automata.

Legendary private island in the Bronx...devoid of rats.

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

Manhattan's lighthouse, erected at the insistence of the unsinkable Molly Brown.

A hyper-luxurious, 12,000- square foot home might be buried beneath Queens, still waiting to protect you from nuclear missiles.

La Monte Young and Marian Zazeela's "Dream House" will immerse you in an ever changing world of sound and light.

Mysterious 500-year-old tapestries depict a unicorn hunt.

Three-story slide through the New Museum.

A room in New York City that contains 250 cubic yards of dirt worth a million dollars.

A hidden "place of interment for gentlemen."

A hip bar decorated with walls of golden skulls.

Feral cats keeping the rodent population at bay all across Greenpoint waterfront.

Rummage through this sunken ship, but leave your scuba gear at home.

Home to the infamous "Typhoid Mary" and the worst loss of life in New York's history prior to September 11, 2001.

A Natural History and Science Emporium.

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

Learn about Iceland's hidden folk at this school dedicated to the study of elves.

Named the fifth most beautiful building in America in 1885, this former courthouse boasts the best view in the Village.