This sculpture by artist Fritz Keonig survived the 9/11 attacks and now stands as a monument to the victims.

Cryptic messages embedded in the New York City sidewalk.

The name of this famed hospital was once a byword for the horrors of medical and psychiatric care.

Manhattan’s Battery Park has a whimsical carousel full of spinning, glowing fish.

The oldest surviving synagogue in New York City is now a soaring art space.

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

This little museum is built on a theater that was once a wildly elaborate speakeasy.

Blighted Irish field and the ruins of a 19th-century cottage on the edge of urban Manhattan.

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

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

Revolutionary War casualties fill the only 17th century structure remaining in Manhattan.

A hidden "place of interment for gentlemen."

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

The remnants of two World's Fairs are here, complete with a 12-story globe, a mini-Manhattan, and a UFO-shaped pavilion.

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

Great place to have a drink and a bite to eat in an atmosphere laden with New York's Bohemian past.

New York City's smallest piece of private property.

Elevated freight railway turned wildly successful urban park.

A historic 1890s architectural masterpiece with an iconic clock tower that, once open to the public, now faces an uncertain future.

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

Try not to get slimed in Tribeca.

A crumbling hospital from the 1850s on Roosevelt Island.

Tucked in the back of this amazing antique store is an important piece of medical history.

New York City's only preserved family home from the 19th century.