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

This hidden oasis features a stunning view of the Hudson River and the Palisades from a castle-like museum.

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

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

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 spooky road cut through a mound of ancient coral might be haunted by a witch.

This Upper East Side apartment co-op was designed as a tuberculosis sanitarium.

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."

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

Wine bottle sculpture with a ship's stateroom inside.

One of the last full-orchestra recording studios in New York City and an acoustical marvel.

Once considered the height of medical modernity, this structure is now the oldest remaining component of Roosevelt Hospital.

From this desk Al Hirschfeld drew his influential caricatures of the 20th century's Broadway stars.

The name of this tiny pocket park tucked between two buildings on Manhattan's Upper West Side is Latin for its location: "seventy-one."

This mosaic dedicated to John Lennon was tended for years by a Beatles super-fan.

Where Greenpoint's first European settler—and troublemaker—made his home.

Red frames showcase remnants of one of New York's original subway stations.

This ruined fort hidden at the top of Central Park can't seem to keep from losing its historical plaques.

This castle-like building in Manhattan helped destigmatize cancer in the 19th century.

A playground the size of a city block is a modernist monument to civic values and public housing.

Peek through the gates at this oasis from the city, full of Old English charm.

Hiroshima survivor on Riverside Drive.

This giant boulder is sandwiched between apartment complexes in upper Manhattan.

A curious fountain that has no water and includes Satan, a crab, and 9 giraffes.