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

Visit the monolithic tomb of America's most famous general.

The famous author's cottage hideaway.

Long the exclusive domain of birds and vagabonds, this little-known Central Park peninsula is open to the public once more.

Curious crustaceans support an obelisk from ancient Egypt that now stands in modern-day Central Park.

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

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

Unique antiquarian shop specializing in globes, maps, and prints.

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

This ruined fort hidden at the top of Central Park can't seem to keep from losing its historical plaques.

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

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

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

Wall Street has a new heroine, a bronze statue of a small but fierce girl.

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

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 Pythagorean funhouse that tries, successfully, to prove that math is the coolest thing ever.

A semi-scholarly approach to sex.

A terrific purveyor of natural history objects and curios.

Tucked in the back of this amazing antique store is an important piece of medical history.

A crumbling hospital from the 1850s on Roosevelt Island.

The oldest of only three existing statues of the great novelist stands in a city he did not care for.

South Philadelphia is home to Keith Haring's only surviving in situ collaborative public mural.