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

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

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

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

The most decorated dog of World War I is preserved in the Smithsonian.

America's oldest Eastern European synagogue provided the immigrants of crowded Lower East Side tenements a space of sanctuary.

The mummified relics of an American missionary.

The former hotel where Tesla invented the radio.

Elevated freight railway turned wildly successful urban park.

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

The rogue roots are gradually consuming some of the historic marble grave markers.

At 207 feet, one of the world's longest continuous escalators.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

An overlooked memorial honoring the local Washington residents who died in World War I.

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

Perhaps the most scandalous statue of America's first president.

The oldest continuously operating fish market in the United States.

An obscure public service from the U.S. government that redeems burnt, moldy, and soiled old greenbacks.

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

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

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

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

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

A museum cafe showcases Native American dishes and indigenous ingredients from across the Western Hemisphere.