While most wind tunnels test scale models, the "Cave of Winds" was large enough for actual airplanes.

The first memorial dedicated solely to the Black troops who fought for the Union.

A bas relief commemorates the "Nuns of the Battlefield" who cared for soldiers on both sides of the conflict.

This forgotten boat elevator was an engineering marvel in its heyday.

Look closely and you’ll notice that the color changes a third of the way up the tower.

Before Nixon, "watergate" meant canals.

A gorgeous mural outside a beloved D.C. restaurant pays homage to famous Black Americans.

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

Members of Congress have traveled between the buildings on Capitol Hill for a century hidden from tourists, press, and storm clouds.

The "lovely red Vega" of the legendary record-settling pilot.

Washington's iconic carousel has a nice piece of Civil Rights history.

Four bald cypress trees in Lafayette Square, across from the White House, mark the southern edge of a 100,000 year old cypress swamp.

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

The most accurate timepiece in the world.

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

The oldest building in the District of Columbia was preserved because of a mistaken connection to George Washington.

A haunting tribute to pioneering photographer Clover Adams.

Home to a vast and influential collection of Shakespeareana.

The first purpose-built art gallery in the United States is once again open as a center of craft arts.

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

The oldest continuously operating fish market in the United States.

The national park was once a plantation estate.

A nostalgic bibliographic gem.

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