A hidden "place of interment for gentlemen."

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.

Townhouse facade doubles as an RMS Titanic Memorial.

A museum collection honoring the long history of the FDNY is held in a disused Manhattan fire house.

The mummified relics of an American missionary.

This whimsical group of statues is a favorite of children who love to climb all over Lewis Carroll's beloved characters.

Visit the monolithic tomb of America's most famous general.

The oldest family-run luncheonette in New York, last renovated in 1948, still serves food and drinks the old-fashioned way.

The oldest surviving synagogue in New York City is now a soaring art space.

An unassuming secret door once led to a legendary watering hole.

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

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

This little museum is built on a theater that was once a wildly elaborate speakeasy.

New York City's smallest piece of private property.

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

Try not to get slimed in Tribeca.

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

A crumbling hospital from the 1850s on Roosevelt Island.

An eccentric inventor's castle home with its own indoor weather system.

A cave dug by a man directed by ghosts to find pirate treasure.

The macabre graffiti spectacle in a quarry in a Massachusetts forest reservation.

The inspiration for H.P. Lovecraft's horror stories and Batman's Arkham Asylum is now a condominium complex.

Ornate and macabre headstone in one of the country's oldest cemeteries.