This abandoned seaside fortress is now simply an imposing ruin being taken back by nature.

An old abandoned mining town in The Adirondacks where Theodore Roosevelt first learned of the shooting of President William McKinley.

The site of the deadly Triangle Shirtwaist Factory Fire.

“Invented in Key West, Perfected in Brooklyn."

The famous author's cottage hideaway.

The factory for the popular Dumbo location, the Greenpoint shop is a quiet gem.

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

This innocent-looking townhome is actually a subway exit.

A discreet little stairway on St. Nicholas Avenue leads to a quaint and unexpected cobblestone street of 19th century wooden rowhouses.

Unrepaired walls from a 1920 anarchist bomb attack.

Sniff the Titan Arum's rotting flesh.

Detailed facade of a brownstone in Boerum Hill.

Reclaimed by nature, the ruins of Doodletown, New York are remnants of a town consumed by a state park.

Avoid gangster interaction while window-shopping.

New York City's only preserved family home from the 19th century.

A bit of retro transportation flair preserved in the world's largest department store.

Cryptic messages embedded in the New York City sidewalk.

Curious crustaceans support an obelisk from ancient Egypt that now stands in modern-day Central Park.

The remnants of two World's Fairs are here, complete with a 12-story globe, a mini-Manhattan, and a UFO-shaped pavilion.

The original toys that inspired the beloved children's stories are on display at the New York Public Library.

A hidden "place of interment for gentlemen."

Lie in a hammock where George Washington stood.

Love, knishes, and best wishes from this legendary Lower East Side bakery.

Behind a bodega is a small museum of relics and ephemera showcasing the history of New York.