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

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

The beautiful tunnel that ran from the lobby to Penn Station is still hidden underneath 34th Street.

Unique antiquarian shop specializing in globes, maps, and prints.

For over 30 years the walls of this Harlem schoolyard have been a gallery of street art by "Kings and better."

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.

Nikola Tesla's former home contains an homage hidden from plain sight.

One of the last Jazz Age "Wonder Theaters" in New York City.

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

A pedestrian island in the middle of world-famous Times Square emits a strange (and purposeful) humming noise.

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

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

A celebration of capitalism in Midtown.

A very classy 1920s-era bar right in Grand Central Station.

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

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

The oldest surviving bridge in New York City, which reopened to pedestrians in 2015.

A masterpiece of LGBT art has been restored in what may now be the most valuable restroom in America.

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

A room in New York City that contains 250 cubic yards of dirt worth a million dollars.

Become a prohibition rebel.

A DIY art gallery/music venue/lecture hall dedicated to video game culture.

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

Under a glass sidewalk lie the remains of some of Manhattan's oldest buildings.