A historic arena where the Beatles played their first concert in the U.S.

The oldest continuously operating fish market in the United States.

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

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

There’s a hidden military meme engraved on the World War II Memorial.

This mysterious structure by the Washington Monument is a flood barrier designed to protect the White House against rising waters.

The grand marble structure next to the White House is Andrew Carnegie's temple to Pan-American diplomacy.

Look closely and you’ll notice that the color changes a third of the way up the tower.

The remains of Martha, the last known passenger pigeon, serve as a tool to educate about conservation.

Washington's iconic carousel has a nice piece of Civil Rights history.

The "lovely red Vega" of the legendary record-settling pilot.

It was once the base for a series of domestic terror attacks.

Home to items never before seen by the public.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

Light bulbs, scrap wood, and tinfoil comprise this homemade throne of the gods.

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

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

The first purpose-built art gallery in the United States is once again open as a center of craft arts.

The national park was once a plantation estate.

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

This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.

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

A tiny piece of the Moon is embedded in this stained glass masterpiece.

The little-known, 300-year history of the area includes former lives as a bustling tobacco port, parking lot, and industrial dump.