The national park was once a plantation estate.

The remains of a historic plantation nestled in between a parking lot and the rental car return at Reagan National Airport.

Please don’t anchor your boat onto the Department of Defense’s underwater data cables.

Collecting 700 years of mechanical death-dealing, the NRA's sprawling gun museum is a revealing testament to the American obsession with armament.

FDR's Art Deco hospital tower was hopelessly inefficient.

The longest escalator in the Western Hemisphere takes over three minutes to ride down.

These recently uncovered walls are all that's left of Washington, D.C's first defense contractor.

The system of air guns are fired off remotely to scare any trespassing avians.

This isn't your average roadway—it's actually a National Park and a transportation pioneer.

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

The oldest continuously operating fish market in the United States.

The only National Monument ever to go missing for nearly 50 years then resurface in a dump.

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

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

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

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

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

One of the largest artillery pieces in the world sits in a Washington D.C. parking lot.

The little-known, 300-year history of the area includes former lives as a bustling tobacco port, parking lot, and industrial dump.

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

Part of a WWII submarine is lurking outside the Washington Navy Yard parking lot.

The grand marble structure next to the White House is Andrew Carnegie's temple to Pan-American diplomacy.

Once forgotten and built over, this historic Black cemetery now houses a poignant memorial.

This simple stone memorial remembers a secret, Geneva Convention-defying interrogation base from WWII.