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

Decades before the scandal, this staircase on the river was a literal "water gate."

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

Rumor has it the hot dog stand was targeted by two Russian nuclear missiles.

The Pentagon is so large that it was planned like a city, complete with internal highway infrastructure.

The national park was once a plantation estate.

Scenic mount trashmore, Virginia Beach's most curious waterfront still has a couple of secrets.

Although built to generate electricity for Marylanders, this dam has become an all-you-can-eat buffet for American bald eagles.

This isn't your average roadway—it's actually a National Park and a transportation pioneer.

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

This pharmacist and his patient greet visitors to the National Community Pharmacists Association.

Once the largest trading firm of enslaved people in the U.S., this building is now a museum that preserves Alexandria's dark past.

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

This brick-lined pedestrian walkway was once a railway tunnel used during the Civil War.

A massive, majestic mammal watches over pedestrians from his perch atop a former B.P.O.E. lodge.

A former major munitions plant that has been converted into a sprawling art space.

This small pedestal marks the spot of the first lot of land sold in Alexandria, Virginia in 1749.

An original apothecary from 1792.

A superbly preserved example of Georgian residential architecture that was once home to one of the founders of Alexandria, Virginia.

This colonial tavern played host to George Washington, Thomas Jefferson, and other famous early Americans.

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 narrowest house in America is seven feet of pure spite.

This 29-ton granite ball spins around at the slightest touch thanks to a scientific phenomenon.

A former Confederate hospital serves as a remembrance of wounded and dead soldiers.