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

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

The only Civil War battle in Washington D.C. took place near this highest natural point in the city.

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

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

At 207 feet, one of the world's longest continuous escalators.

This church built atop a gas station promises to "equip you for the next stage in your life’s journey."

This unique historical monument features large concrete spheres designed to resemble fallen stars.

An oft-overlooked, magically musical monolith that stands majestically between Arlington Cemetery and the Iwo Jima Memorial.

The rogue roots are gradually consuming some of the historic marble grave markers.

Born a slave on the Arlington estate, Parks dug the first graves at Arlington National Cemetery, and was buried there, too.

The naval commander’s proudest moment in battle is memorialized in this unique tomb at Arlington Cemetery.

Recorded as the first person buried in Arlington Cemetery.

Though his role as the inventor of baseball may be up for debate, fans still festoon Doubleday's grave with baseballs.

In what is rumored to be an intentional act of spite, this memorial almost completely obscures the nearby grave of a senior officer.

A gift from Scotland to the United States in memory of the 270 lives lost when Pan Am Flight 103 exploded over Lockerbie due to a terrorist bombing.

The controversial urban planner who designed Washington, D.C., was buried in Maryland, and can presently be found in Virginia.

Soldiers were buried next to Lee's house in the center of Arlington Cemetery to dissuade the general from reclaiming his property after the war.

Housing the National Women's Party since 1929, this historic house is now a monument to the fight for gender equality.

This groundbreaking 16th-century map is known as "America's birth certificate."

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

After his presidency, George Washington planned to live only a few blocks from the Capitol building.

An unassuming, powerful monument north of the U.S. Capitol bears witness to the resilience of Japanese Americans during a time of grave injustice.

The tunnel under the Capitol Building where Congress takes out its trash.