A large boulder marks the place where the island of Manhattan was purportedly "sold" to the Dutch.

This elaborate tunnel is the first structure composed of cast concrete in the United States.

The greatest real estate coup of all time.

A forgotten relic from New York's bygone trolley system hides in plain sight under a bridge.

This was one of the first (and last) university-built and operated nuclear reactors.

A grand New York post office that is home to mailman Santas, scraps of postal history, and a pneumatic mail system.

Abandoned 19th century homes once occupied by naval officers, soon to be demolished.

In 1986, Keith Haring was arrested for painting this anti-drug mural on a Harlem handball court.

The site of a fallen tree that protected Americans from British forces during the American Revolution.

If it hadn't been caught in time, a flaw in the design of this Manhattan skyscraper could have led to its collapse.

Sip a cappuccino in the historic cafe that introduced them to the United States.

While it now takes more than a dime to open an account this historic Brooklyn bank still displays the opulence of the gilded age in which it was built.

This beautiful Brooklyn monument over a crypt memorializes a grim and largely unknown story from the American Revolution.

New York's southernmost subway station is whimsically wavy.

A replica of a 7th-century church hides in plain sight in the middle of the concrete jungle.

The smallest island in Manhattan is a manmade landfill dominated by a Buddhist peace arch.

This memorial honors thousands of enslaved Africans and their descendants who died in colonial New York.

Hiroshima survivor on Riverside Drive.

Every year model trains zip through a miniature New York City that's now 150 landmarks strong.

One of only two remaining Victorian-era greenhouses in New York.

This innocent-looking townhome is actually a subway exit.

An uber-secure, windowless tower of doom in the center of Manhattan is an NSA spyscraper.

Once the tallest building in the world and the site of "the highest dinner ever held in New York" this building now holds the most expensive penthouse in the city.

Wall Street has a new heroine, a bronze statue of a small but fierce girl.