An overlooked tribute to one of the most important peace deals in American history.

A memorial to a shareholder activist feared by CEOs around the United States.

Amid the sprawling Defense Intelligence Agency Headquarters is one of Washington's least accessible museums.

This unassuming passageway played a key role in one of the most important events in U.S. history.

‘Bush the old fire dog died of poison July 5th, 1869. RIP.’

More than 500 unique and specially designed cases collected by D.C.'s "Harmonica Case Man."

The first memorial dedicated solely to the Black troops who fought for the Union.

A small token of gratitude from freezing cold journalists who were given a warm haven while covering JFK's inauguration.

Was there a small "backpack nuke" hidden in the attic? JFK apparently thought so.

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

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

For 60 years, the academy had no permanent location until members voted Washington D.C. as its forever home.

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

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

This unique museum cafeteria showcases the history and regional diversity of African American cuisine.

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.

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

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.

Sit where JFK proposed to Jackie or where Nixon dined on meatloaf at this storied pub.

100 years later, they're still down there.

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

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