A once grand hotel is being retaken by the wilderness it once capitalized on.

The "Seinfeld" diner.

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

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

From scholastic to sepulchral - now under reconstruction.

Hidden in plain sight on a pair of Manhattan subway tunnels are a pair of public instruments that sing to each other.

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

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.

The oldest operating apothecary in the US has treated everyone from Thomas Edison to Mark Twain.

Tucked away amidst some of the most famous addresses in the world is New York's only fraction of a street.

This whimsical group of statues is a favorite of children who love to climb all over Lewis Carroll's beloved characters.

An unassuming secret door once led to a legendary watering hole.

A natural gas leak provides a flickering flame beneath a waterfall.

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

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

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

The world's oldest hologram gallery and the labyrinthine laser laboratory of a holography pioneer.

A three-story copper skybridge connects two Manhattan buildings with Art Deco luxury.

Hidden in Central Park's Ramble is a troublesome cave buried just beneath the surface.

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

Hidden in an ordinary Midtown building is a one-room museum dedicated to the greatest escape artist.

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

A tunnel once abandoned now thrives with graffiti art as an off-limits makeshift gallery.

The abandoned husk of a mental institution that failed to save a Jazz Age icon still sits nearly unchanged.