This castle-like building in Manhattan helped destigmatize cancer in the 19th century.

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

Once considered the height of medical modernity, this structure is now the oldest remaining component of Roosevelt Hospital.

A dark patch of the ceiling at Grand Central Terminal which was not restored is still stained brown by tobacco.

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

Though its celestial ceiling is impressive, the true star is the vast collection of French books.

The "Seinfeld" diner.

A dark, dank room in subterranean Manhattan was the site of a ghastly murder.

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

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

This cemetery has graves dating back to the 17th century, including the city's oldest carved tombstone and an ominous cryptogram.

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

A pedestrian island in the middle of world-famous Times Square emits a strange (and purposeful) humming noise.

A dilapidated dock tells the story of Titanic's missed arrival.

Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.

A hip bar decorated with walls of golden skulls.

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

This abandoned subway station beneath the Waldorf-Astoria hotel is allegedly used to secretly transport presidents.

Try not to get slimed in Tribeca.

This beautiful building in the heart of Manhattan's Financial District was empty for decades.

A treasure trove of artifacts, books, and artwork from the "golden age" of exploration.

A crumbling hospital from the 1850s on Roosevelt Island.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

An extraordinary mixture of natural beauty and man-made phenomena.