This unassuming passageway played a key role in one of the most important events in U.S. history.

A rotating cast of guys and dolls in front of a Washington, D.C. building.

D.C. once had its own tiny rival to the New York Stock Exchange.

This nine-story building is the oldest standing skyscraper in D.C.

This stunning blue and gold room changed cities twice before becoming part of the Smithsonian.

This whimsical outsider art wall holds tiny treasures donated by the local community.

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

The national park was once a plantation estate.

An unusual sculpture, an interesting history, in a strange place, for a good cause.

The world's oldest continuously operating airport was founded by the Wright Brothers.

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.

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

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

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

The narrowest house in America is seven feet of pure spite.

D.C.'s first central library was born out of a chance encounter with the philanthropist whose name it bears.

The unique traffic pattern named for an influential urban planner is also known as the Pedestrian Scramble.

This little brick tunnel built by Confederate forces was used to conduct surprise attacks on the railroad.

A state park that once served as an important river crossing, and now offers protected lands for endangered plants and animals.

A building shaped like the Army Corps of Engineers logo, because why not?

This Boeing KC-97 tanker is now a restaurant for aviation lovers.

This lovely picnic spot featuring thunderous jet landings is an aircraft spotter’s dream.

Thomas Jefferson's estate is home to hundreds of varieties of historic fruits and vegetables.

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