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.

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

Rummage through this sunken ship, but leave your scuba gear at home.

This slender three-story building has also had several famous residents.

Twenty-three trees, each paired with a basalt stone, line a street in Chelsea, continuing an urban project started by German Fluxus artist Joseph Beuys.

Manhattan's deadly West Side railroad, which killed hundreds of New Yorkers, is remembered by this simple plaque.

Avoid gangster interaction while window-shopping.

Berliners converted a bombed-out, disused lot into a community-run urban farm with its own cafe and bar.

The footprint of a frustrated devil in Munich's Cathedral.

Golden cobblestones remember a time when this small alley was used to avoid having to give a Nazi salute.

The patron saint of spinsters grasps a container of dried blood.