A glimpse at Walt Disney's vision for a "community of tomorrow," in miniature.

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

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

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

One of the three perfect vellum copies of this historic book known to exist is on display in a specially-designed case.

Railroad officials in the early 1900s sought to spare travelers the sight of Roman soldiers’ private parts.

A 1,100-ton train fell through the floor in 1953. Workers got it patched up in just 72 hours.

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

"Congress may voluntarily remain in session throughout the summer, in order that our Congressmen may be protected from the intolerable discomforts and dangers of the ordinary outdoor weather!”

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.

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

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

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

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

The U.S. Fish Commission’s effort to mass produce carp.

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

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

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

A priceless collection of the Nation's cryptologic history.