The only Leonardo Da Vinci painting in the Western Hemisphere.

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.

This taxidermy horse was a Civil War hero.

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

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

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

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

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

Architecture lovers won’t stop touching the National Gallery's 19.5 degree marble prow.

A small triangle of DC grass is the final resting place of one of Sonny and Cher's songs.

The preamble to the U.S. Constitution written entirely from vanity license plates hangs in the Smithsonian museum.

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

Light bulbs, scrap wood, and tinfoil comprise this homemade throne of the gods.

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.

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

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

The unique traffic pattern named for an influential urban planner is also known as the Pedestrian Scramble.

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

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

Home to items never before seen by the public.

The highest point in Tennessee, Clingmans Dome bears witness to the ravages of one type of insect.

This vast kitty-themed collection illustrates the history of human-cat interaction.

Mysterious ancient boulder carved with petroglyphs in the mountains of Western North Carolina.

Turning night into day in Victorian-era Austin to thwart a serial killer.