This "castle" is actually a limestone and quartz formation hidden along a trail.

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

Please don’t anchor your boat onto the Department of Defense’s underwater data cables.

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.

Recorded as the first person buried in Arlington Cemetery.

The Pentagon sits on a former island that was in Virginia at low tide and D.C. at high tide.

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

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.

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

Now a living classroom, this house was once the home of Reverend James Clinton Dent, a formerly enslaved man and a pastor.

Long buried under the 20th-century landscape, this lift lock of the Alexandria Canal is the lone remnant of an ambitious early American transportation project.

The "Sultan of Swat" once attended a school at the site of this baseball field.

A small and somewhat hidden memorial to 68 local veterans of the Vietnam War.

The former home of the woman who successfully fought to integrate restaurants in Washington, D.C.

Washington D.C.'s most famous pianist, composer, and bandleader still tickles the ivories outside Howard Theater.

A 14-foot monument marks the resting place of two of the town's earliest residents—and one unknown soldier.

The former home of Lillian Evans Tibbs and her grandson, Thurlow Evans Tibbs Jr., whose prodigious contributions to music and art spanned more than 90 years.

Built to defend Washington D.C. during the Civil War, this fort became a post-war nucleus for a thriving Black community.

The world's oldest soul food restaurant is also one of its best.

Home to two notable early-20th-century Black educators, Lucy Slowe and Mary Burrill.

One of the first Second Empire-style buildings constructed in North America.

"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!”

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.