Decades before the scandal, this staircase on the river was a literal "water gate."

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

The oldest continuously operating fish market in the United States.

Government testing at the asylum briefly explored using marijuana as a "truth serum" on Nazi prisoners of war.

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

When it opened during the final years of the embargo, all the drinks and cigars were free.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

A historic estate packed with George Washington's heirlooms, and its own nuclear bunker.

A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

A derelict bit of transportation infrastructure hidden in the woods.

During the Industrial Revolution this “Temple of Invention” was full of intricate miniature machines and gadgets.

A lovely aquatic park built by a one-armed Civil War veteran who made a fortune from lotuses.

Home to items never before seen by the public.

The site of the climactic scene from the classic horror film is now a historic landmark.

A portal into the bricked up canal that runs through the heart of Washington D.C.

Go take a picture with the inventor of the daguerreotype photographic process.

America's Most Wanted's set resides in this tribute to the history of crime and punishment.

A much-maligned monument to teetotalism.

The winding route passes through an enclosed alleyway, two tunnels, and leads to the White House basement.

A muscular Art Deco monument represents the struggle between regulators and unbridled markets.

The bank that helped fund the Mexican-American War and the purchase of Alaska met its downfall after helping Augusto Pinochet launder money.

This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.

Before Nixon, "watergate" meant canals.