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

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

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.

"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!”

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

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

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

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

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.

Daily lunch spot for many of Washington, D.C.'s cab drivers.

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

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

Before Nixon, "watergate" meant canals.

100 years later, they're still down there.

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

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

This forgotten boat elevator was an engineering marvel in its heyday.

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

A historic arena where the Beatles played their first concert in the U.S.

This unacceptably tall building was the real reason for Washington, D.C.'s skyscraper ban.

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

The only National Monument ever to go missing for nearly 50 years then resurface in a dump.