One of the few remaining American elm trees in New York’s Tompkins Square Park was the birthplace of a new religion.

A staggering collection of photographs depicting medical, social, and historical change.

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

A quiet and contemplative oasis in the middle of New York's bustle and riot.

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

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

A dilapidated dock tells the story of Titanic's missed arrival.

This lower Manhattan bar is set up in an old bank vault that rests beneath a skyscraper that hides even more historic splendor.

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

This abandoned subway station beneath the Waldorf-Astoria hotel is allegedly used to secretly transport presidents.

Dodge prohibitionists and slide through the telephone booth in Crif Dogs.

La Monte Young and Marian Zazeela's "Dream House" will immerse you in an ever changing world of sound and light.

With a history of slaughter, feast, and famine, remnants of the pork industry decorate this area--even its church.

Down a cobblestone alleyway is a museum dedicated to Romanticism, with a secret garden.

A counter-culture bookstore like no other hides in plain sight in the streets of Paris.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

The oldest stone house in Paris was built by its most famous alchemist.

A mechanized clock where a man fights off a dragon, crab, and rooster.

Notorious artist squat renovated into legal studios.

A small island less than half a mile from Venice is a forbidden island with a dark and twisted past.

This community on a small Venetian island has taken to painting their houses in bright neon hues.

Venice's "Island of the Mad."

Go inside to really appreciate this 500-year-old technological masterpiece.

Monsters and miniatures are held in equal esteem at this wondrous museum.