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

Possible relics of the ancient Roman city are hidden in this restaurant's façade.

Where now stands a 42-story condominium tower of marble, glass and steel was once the central market of New York’s slave trade.

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

Amid the bustle and noise of the Financial District hides a secluded garden oasis above the city streets.

Twice a day one of these tragic bronze mariners drowns with the tide to remember all those the sea has taken.

The home of the first American-born saint is one of the only curved buildings in New York.

A plaque immortalizes the spot where the early American spy said his famous last words: "I only regret that I have but one life to lose for my country."

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

The oldest bibliophilia club in America, with exhibitions on historic books and graphic arts.

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.

New York's oldest and possibly grandest keeper of books.

The front yard of an Upper East Side town house hides the last fragment of one of New York's most famous theatres.

The walls are decorated with whimsical murals painted by the creator of the Madeline franchise.

The oldest family-run luncheonette in New York, last renovated in 1948, still serves food and drinks the old-fashioned way.

A Victorian cemetery in the heart of Brooklyn remains a popular mecca of morbid curiosity.

Elevated freight railway turned wildly successful urban park.

A crumbling hospital from the 1850s on Roosevelt Island.