A historic estate packed with George Washington's heirlooms, and its own nuclear bunker.

A lovely aquatic park built by a one-armed Civil War veteran who made a fortune from lotuses.

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

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

The iconic D.C. restaurant where the Cuban Missile Crisis was negotiated, now a Walgreens.

America's Most Wanted's set resides in this tribute to the history of crime and punishment.

This statue of the "father of television" stands prominently in the United States Capitol.

D.C. once had its own tiny rival to the New York Stock Exchange.

Disks are rolled out onto the south lawn to absorb the impact of Marine One's wheels like giant coffee coasters.

The U.S. Navy’s preposterously detailed mini battleship took 77,000 hours to complete.

An ear-piercing buzzer calls lawmakers to a vote with a series of long and short rings to form coded messages.

A promising candidate for the lost rock laid by George Washington was unearthed, but the hunt is still on.

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

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

During Prohibition, the U.S. Congress had an "official" bootlegger, with his own Capitol Hill office.

The school tested mustard gas for the U.S. Army during World War I.

The early data processor factory founded in Washington for the 1890 U.S. Census went on to become IBM.

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

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

A building shaped like the Army Corps of Engineers logo, because why not?

Home to a vast and influential collection of Shakespeareana.

A diminutive plaque recalls the treetop sniper who almost killed Abe Lincoln.