A crumbling hospital from the 1850s on Roosevelt Island.

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

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

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

A little lighthouse in New York City, surrounded by mysterious stories of insanity-driven construction.

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

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

This monument to a veteran of the Mexican-American War is one of only two in Manhattan that serve as an actual mausoleum.

A Manhattan courthouse hides a small but scathing memorial to Holocaust injustice.

There are owls with glowing eyes in Herald Square.

The 28-foot granite map plots the locations of 40 theaters in New York City.

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

Built hundreds of years ago this downtown iron barrier once protected a much despised king.

Phil Mortillaro uses keys to bring art back to the Village.

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

Rat sculptures try to infiltrate the Graybar Building in an architectural tribute to New York City's nautical history.

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

Spinning silently in the lobby of an Art Deco masterwork is a massive vintage model of the Earth.

There must be a pun in this haystack somewhere...

This simple Manhattan salt house is artfully shaped... well, like a giant granule of salt.

These ornate manhole covers were used for a now-forgotten purpose.

The first piece of public art dedicated to LGBT rights.

New York City's smallest piece of private property.

Manhattan's Thirteenth Avenue was made on landfill then deliberately destroyed — apart from one small, obscure block.