This massive swimming pool is the high tech home to the human-powered submarine races.

This site is believed to be connected to the oldest house in Arlington County.

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

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

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.

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

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

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

This cannon dating to 1755 has stood guard at this suburban intersection since 1915.

An original apothecary from 1792.

The final resting place of an unidentified revolutionary soldier sits behind a Virginia church.

Once forgotten and built over, this historic Black cemetery now houses a poignant memorial.

This grave marks the passing of a historic Jane Doe whose identity remains a mystery to this day.

This simple stone memorial remembers a secret, Geneva Convention-defying interrogation base from WWII.

Remains of a historic fountain that was mysteriously lost in the demolition of a D.C. traffic circle.

This fort down the Potomac from Washington, D.C. was once the only defensive fort protecting the capital.

The 72-foot giant escaped confinement in a large patch of mulch only to be reburied in the sandy shores of the Potomac River.

This rare triple-jurisdiction drawbridge passes through Virginia, Maryland, and Washington, D.C.

America's first federal monument.

The former home of Thomson Francis Mason, the mayor of Alexandria from 1827-1830.

Dedicated to a U.S. Army lieutenant colonel who was also a bird watcher and artist.

The U.S. Army's giant warehouse of war art includes Hitler’s watercolors and Norman Rockwell oil paintings.

This church is known as "The Home Church of George Washington and George Mason."