Harlem park dedicated to compulsive hoarders killed by their own junk.

Empty, but not abandoned, this cavernous Brooklyn loading dock was once considered the largest individual building in the world.

More than 300,000 historical artifacts from the famous music venue, from Duke Ellington's handwritten score to The Beatles' booking slip.

An oasis of calm amid the chaos of the boardwalk, the museum traces the heritage of this beloved beachside amusement park.

The site of the deadly Triangle Shirtwaist Factory Fire.

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

There’s a secret bunker inside the Brooklyn Bridge, but the city won’t say where.

The famous author's cottage hideaway.

This hidden library of physiological ephemera contains centuries worth of knowledge on the vim and viscera of the human body.

Tucked in a nondescript downtown Brooklyn mall is a bar containing a remarkable turn of the century anatomical wax collection last seen in 1920s Berlin.

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

The oldest bibliophilia club in America, with exhibitions on historic books and graphic arts.

This mosaic dedicated to John Lennon was tended for years by a Beatles super-fan.

The beautiful tunnel that ran from the lobby to Penn Station is still hidden underneath 34th Street.

The oldest house in Manhattan is now a museum that remembers the home's sordid history of scandals, vice-presidents, and ghosts.

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

The "Seinfeld" diner.

The name of this famed hospital was once a byword for the horrors of medical and psychiatric care.

The world's oldest hologram gallery and the labyrinthine laser laboratory of a holography pioneer.

A DIY art gallery/music venue/lecture hall dedicated to video game culture.

Hidden in Central Park's Ramble is a troublesome cave buried just beneath the surface.

A legendary speakeasy bookstore returns from the brink.

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

The world’s oldest and biggest bookstore stocking only mystery, crime fiction, espionage, and thrillers.