This Rhode Island mansion was a stand-in for the exteriors of Collinwood in the original "Dark Shadows" series.

The oldest still-operating tavern in the United States was once owned by a pirate.

A crumbling stone stable and carriage house are all that remain of a manse that was once filled with Egyptian artifacts.

A single light illuminates one man's overshadowed contributions to street lamp history.

Three and a half miles of cliffs, rocky beaches, Gilded Age mansions and 40 Steps to nowhere in particular.

Mysterious stone tower featured in many alternative histories of the New World.

Oldest synagogue in the United States.

The home of the artist credited with introducing the tomato to the American diet.

The second oldest Jewish graveyard in the U.S. is tiny, with connections to George Washington and Henry Wadsworth Longfellow.

This historic Rhode Island mini-cemetery features a number of headstones run through with mysterious holes.

A tunnel with windows, so you don't miss out on the impressive views.

This palatial botanical garden is home to one of the largest pipe organs ever installed in a private residence, and a piece of Wood's cycad.

These lush botanical gardens employ the most purrfect pest control force.

A tour de force of a fountain, memorializing a man who loved fountains more than anything else.

This beloved marketplace mascot poops money and grants good luck.

The origin of this mechanical boy was a mystery until he revealed his maker by writing it in perfect cursive.

Golden and naked, the figure that was once the highest point in New York is all that remains of the second Madison Square Garden.

One artist's love letter to his city and its citizens plays out across dozens of bright murals painted on the sides of decrepit buildings.

The semi-reclaimed ruins of this canal were once part of an ambitious plan to reroute the mighty potomac.

The U.S. Fish Commission’s effort to mass produce carp.

A tiny monument to the unsuccessful attempt by Thomas Jefferson to place the prime meridian in Washington.

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

There’s a hidden military meme engraved on the World War II Memorial.

This mysterious structure by the Washington Monument is a flood barrier designed to protect the White House against rising waters.