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

Tucked away amidst some of the most famous addresses in the world is New York's only fraction of a street.

Sniff the Titan Arum's rotting flesh.

The "Seinfeld" diner.

The oldest surviving bridge in New York City, which reopened to pedestrians in 2015.

Mysterious 500-year-old tapestries depict a unicorn hunt.

A three-story copper skybridge connects two Manhattan buildings with Art Deco luxury.

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

Ride the subways of yesteryear.

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

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

Elevated freight railway turned wildly successful urban park.

A crumbling hospital from the 1850s on Roosevelt Island.

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

A former waterfront market is now in the center of town due to some interesting Boston engineering.

Mrs. Mallard and her brood are a beloved fixture in Boston Public Garden.

One of the oldest used bookstores in the U.S. has been selling antiquarian treasures since 1825.

This distinctive Crescent City tradition dates back to the days of horse-drawn carriages.

This historic "City of the Dead" lies prominently in the center of New Orleans' famous Garden District.

The place where Samuel "Slater the Traitor" brought the Industrial Revolution to America.

The first ever diner included on the National Register of Historic Places is famous for its custard French toast.