A mammoth pair of Civil War artillery guns abandoned out in the forest.

The longest escalator in the Western Hemisphere takes over three minutes to ride down.

This stately building in Alexandria, Virginia was built by Freemasons to honor one of their most famous members.

A diminutive plaque recalls the treetop sniper who almost killed Abe Lincoln.

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.

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

The United States Capitol's former columns still stand.

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.

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

This leafy estate is worth $18 million and is so grand it has two mailing addresses.

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.

The most accurate timepiece in the world.

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

The site of the climactic scene from the classic horror film is now a historic landmark.

This lonely waterfront memorial to the men of the Titanic was erected by the "Women of America."

There's a crumbling old mansion inside the Smithsonian National Zoo.

A historic estate packed with George Washington's heirlooms, and its own nuclear bunker.

A nostalgic bibliographic gem.

This robust fence in front of a historic Georgetown home is likely made from hundreds of recycled Revolutionary War firearms.

This lovely pocket park is one of the most under appreciated in D.C.

A fantastic array of trays and cables once whisked books over to the Capitol at 600 feet per minute.

People escaping slavery may have hidden inside a corpse vault.

The walls of the iconic dome are hollow and have a secret stairway.