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.

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

The monument's pointy aluminum tip has been melted down by repeated lightning strikes.

Daredevil repair workers can worm their way out the access hatch, loop ropes over the apex and rappel down the monument.

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

The national park was once a plantation estate.

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

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

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

A heroic pigeon that, through a barrage of gunfire, delivered a message that saved over 100 lives in World War I.

This taxidermy horse was a Civil War hero.

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

A computer bug so primitive it was an actual insect.

This sandwich shop has a century-old elevator behind a sheet of plexiglass.

Need a hardcopy of the 50-title Code of Federal Regulations? This is the place.

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

The house where John Wilkes Booth conspired with his co-conspirators.

Before Nixon, "watergate" meant canals.

A line of blue paint marks the route of the inaugural parade.

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

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

This robust fence in front of a historic Georgetown home is likely made from hundreds of recycled Revolutionary War firearms.

The sculptor was instructed to add “stallion attributes” to the general's bronze mare.