Once America's longest-manned military fort, now an abandoned hulk.

Unlock the secrets of the conjuring arts.

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

The loneliest island in New York.

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

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

Read between the lines of the subway map to find the hidden abandoned Civil War fort.

Home to the infamous "Typhoid Mary" and the worst loss of life in New York's history prior to September 11, 2001.

This unmarked and unloved Manhattan subway grate created one of the most iconic images in American cinema.

The "Seinfeld" diner.

Sniff the Titan Arum's rotting flesh.

Read a book next to a Midtown waterfall.

The feral felines of Roosevelt Island have a small army of allies and an abandoned hospital all to themselves.

A miniature rainforest is growing inside of a Midtown Manhattan office building.

Try not to get slimed in Tribeca.

The world’s oldest and biggest bookstore stocking only mystery, crime fiction, espionage, and thrillers.

There's an old indoor swimming pool hidden directly underneath the White House Press Briefing Room.

Light bulbs, scrap wood, and tinfoil comprise this homemade throne of the gods.

Seemingly unremarkable items like empty sushi trays, chef hats, and freshness stickers are being preserved so future generations can look back on this beloved cultural import.

A super-sized promotional trick that is now a D.C. landmark.

A rotating cast of guys and dolls in front of a Washington, D.C. building.

This lonely waterfront memorial to the men of the Titanic was erected by the "Women of America."

This stunning blue and gold room changed cities twice before becoming part of the Smithsonian.

A painfully obvious spy house sits right across the street from the Russian Embassy.