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

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

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

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

Go take a picture with the inventor of the daguerreotype photographic process.

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

The remains of Martha, the last known passenger pigeon, serve as a tool to educate about conservation.

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

A haunting tribute to pioneering photographer Clover Adams.

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

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

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

The real-life site of Ichabod Crane's infamous gourd attack.

Oldest existing church in New York and the inspiration for Washington Irving's "The Legend of Sleepy Hollow."

Haunted Victorian house that inspired a legendary "Ghostbusters" court ruling.

A historic Black graveyard hidden in the parking lot of one of America's largest malls.

This house was the subject of an Edward Hopper painting, which in turn helped inspire the design of the Bates house in Alfred Hitchcock's 'Psycho.'

Decades after testing the polio vaccine on unwitting patients, this historic mental hospital sits in ruin.

An ode to "The Queen of Appalachia."

While knives are the main feature in this store, visitors will also find dinosaur bones and meteorites.

An abandoned town is hidden in Great Smoky Mountains National Park.

A life-sized memorial to Harry L. Collins, the official corporate magician of Frito-Lay.

The Midwestern United States' tribute to Michelangelo is a foam statue sprayed with gaudy gold paint.

The largest cemetery in Louisville is the final resting place of Col. Sanders and Muhammad Ali.