A crumbling hospital from the 1850s on Roosevelt Island.

Site of the first pathological and bacteriological research facility in the United States.

The feral felines of Roosevelt Island have a small army of allies and an abandoned hospital all to themselves.

A former insane asylum despised by Nelly Bly and Charles Dickens is now fashionable apartments.

A sculptural commentary on capitalism pokes up from the East River.

On this island, you suck away your garbage via an elaborate pneumatic tube system.

One of only two commuter aerial tramways in the United States.

A commemorative plaque hides a door that leads down to the New York Public Library's underground book bunker.

An homage to Jackie Gleason's bus-driving character from 'The Honeymooners.'

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

Fake subway tiles were installed to cover a design that resembled the Confederate flag—it's unclear if the resemblance was intentional.

This stone gatehouse was once the entrance to a historic mountain resort, and it had a cameo in a cheesy cult horror movie.

Currently housing a corporate bank branch this building at the southern tip of Manhattan was once the gateway to luxury vacationing.

The oldest family-run luncheonette in New York, last renovated in 1948, still serves food and drinks the old-fashioned way.

The front yard of an Upper East Side town house hides the last fragment of one of New York's most famous theatres.

This whimsical group of statues is a favorite of children who love to climb all over Lewis Carroll's beloved characters.

Hidden behind a gate in Greenwich Village is a little farmhouse that once served as the writing studio of a bestselling author.

Great place to have a drink and a bite to eat in an atmosphere laden with New York's Bohemian past.

Surrounded by low rise buildings and partially converted into an auto body shop, this marble archway is the only vestige of a forgotten Manhattan estate.

This Dutch Colonial home is the oldest remaining farmhouse in Manhattan.

Gang fights don't just happen on the streets, they happen under them too.

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

Cheap pizza and all of your naughty bedroom needs housed in a stunning example of Art Nouveau architecture.

Those belting out show tunes might not realize this piano bar marks the site where Thomas Paine died in 1809.