A former insane asylum despised by Nelly Bly and Charles Dickens is now fashionable apartments.

The former hotel where Tesla invented the radio.

This collection of grinning ephemera has grown from basement to Brooklyn.

Cryptic messages embedded in the New York City sidewalk.

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

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

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

A hands-on traveling collection of the innovative devices of yesteryear.

Reverend Jen's unique museum/living room showcases her troll collection.

This abandoned subway station can still be seen on regular commuter trips.

Lie in a hammock where George Washington stood.

A dark, dank room in subterranean Manhattan was the site of a ghastly murder.

Wall Street has a new heroine, a bronze statue of a small but fierce girl.

Deep under Manhattan is the largest construction project in city history. So far, the project has taken the lives of 23 workers, or "a man a mile."

A popular European tradition makes its way to the states on one of America's most famous bridges.

A living archive of urban activism and space reclaimed.

Walk over a 150 year old manhole.

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

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

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.

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

One of the last few places in Manhattan that employed a pneumatic systemic keeps it on display.

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

A historic 1890s architectural masterpiece with an iconic clock tower that, once open to the public, now faces an uncertain future.