Two stunning 17th-century libraries and a cabinet of curiosities.

Collapsing castle on the Hudson river was once the storage site of military surplus business.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

Try not to get slimed in Tribeca.

A swing to dangle you off the very edge.

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

A tiny museum housed in a New York freight elevator specializes in the "overlooked, dismissed, or ignored."

America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

A huge musical instrument played by the ocean.

A crumbling hospital from the 1850s on Roosevelt Island.

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 beautiful and abandoned New York subway station from 1904, complete with chandelier.

The humble horn finally finds a place in the sun.

Conjoined twins Daisy and Violet Hilton were stars of the vaudeville circuit.

A much-maligned monument to teetotalism.

Built as a gift to the hottest tastemaker of the time, these hidden quarters remain an Art Deco showpiece.

Wine bottle sculpture with a ship's stateroom inside.