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

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.

A diminutive memorial marks the site of a successful assassination by a right-wing death squad in America's capital.

Before Metro, Washington had a robust streetcar network—and you see the remains of this infrastructure if you know where to look.

This nine-story building is the oldest standing skyscraper in D.C.

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

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

Before founding the American Red Cross, Clara Barton had a tremendous humanitarian impact by locating thousands of missing soldiers.

The fountains of the U.S. Navy Memorial are annually salted with water from the Seven Seas as part of a nautical ritual.

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

They sort through millions of dollars worth of diplomatic gifts on behalf of the government.

Senators used to relax in the nearly forgotten marble tubs now hidden in the U.S. Capitol Building's basement.

Washington's top-secret Cold War-era doomsday communications tower is located in a small neighborhood park.

Home to a vast and influential collection of Shakespeareana.

When it comes to handsignals (and colonialism) rock always beats scissors.

There just so happens to be a court even higher than the U.S Supreme Court: a basketball court in the building itself.

A bas relief commemorates the "Nuns of the Battlefield" who cared for soldiers on both sides of the conflict.

There's an old indoor swimming pool hidden directly underneath the White House Press Briefing Room.

"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!”

Before Nixon, "watergate" meant canals.

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

Helen Keller once broke ground on this historic center for the study of technologies to benefit the hearing impaired.

100 years later, they're still down there.