This beautiful building in the heart of Manhattan's Financial District was empty for decades.

The façade of this building looks like a bingo board, but it's really a giant clock by a famed graphic designer.

New York City's first Modernist house.

Though its celestial ceiling is impressive, the true star is the vast collection of French books.

This lavish room at NYC's French Embassy is a rare relic from the end of the Gilded Age.

An aptly-named street near the birthplace of the modern LGBT rights movement.

The highest point on the island known for buildings that touch the sky.

Storage warehouse of the rich and famous.

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

A well-worn marker in a forgotten alleyway is all that remains of what had been one of Manhattan's most beautiful buildings.

Currently housing a corporate bank branch this building at the southern tip of Manhattan was once the gateway to luxury vacationing.

Surrounded by low rise buildings and partially converted into an auto body shop, this marble archway is the only vestige of a forgotten Manhattan estate.

This Dutch Colonial home is the oldest remaining farmhouse in Manhattan.

This curved Manhattan building was built to house the opulence of John D. Rockefeller's oil empire.

Built hundreds of years ago this downtown iron barrier once protected a much despised king.

This anonymous businessman sculpted in bronze became an enduring memorial after 9/11, and had been mistaken by rescue workers for a survivor in the rubble.

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

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

The 28-foot granite map plots the locations of 40 theaters in New York City.

Built as a gift to the hottest tastemaker of the time, these hidden quarters remain an Art Deco showpiece.

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

The crown jewel of the Queens Museum is a nearly 10,000-square-foot architectural model of the city originally built for the 1964 World's Fair.

This unmarked and unloved Manhattan subway grate created one of the most iconic images in American cinema.

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