Hidden in plain sight on a pair of Manhattan subway tunnels are a pair of public instruments that sing to each other.

Hidden in an ordinary Midtown building is a one-room museum dedicated to the greatest escape artist.

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

A celebration of capitalism in Midtown.

Hundreds of antique bank vault locks on display in New York City.

Down a stairway in the East Village, you could once read a plaque describing an alternate history of a fictional version of Manhattan.

Volunteer-run library dedicated to exploring five decades of activism history.

A tree that grows parallel to the ground was declared Brooklyn's "crowning curio" by the poet who saved it.

This otherwise innocuous bodega was once the headquarters of the most feared assassin's guild in American history.

Manhattan and the Bronx have been playing tug-of-war over this former island neighborhood for more than a century.

The first "Hall of Fame" in America was designed by legendary Gilded Age architect Stanford White for what was then the NYU uptown campus.

Nondescript elevator doors open to reveal a stunning, surreal world.

The preserved house of a jazz legend still echoes with his music.

A long abandoned hospital building on the outskirts of NYC.

A Manhattan office building is home to the world's largest chess board.

A WWI fighter plane and turn-of-the-century penny candy shop are among the unexpected features of this Financial District building.