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

The romance of early commercial flight still fills this Art Deco destination.

The oldest continuously operating fish market in the United States.

While most wind tunnels test scale models, the "Cave of Winds" was large enough for actual airplanes.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

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

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

On the Fourth of July this area will transform into a Pompeii-like storm of falling embers and ash.

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

This unique museum cafeteria showcases the history and regional diversity of African American cuisine.

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

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

Before Nixon, "watergate" meant canals.

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

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

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

This grand gothic brewery has been pumping out suds for over a hundred years.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

Largest Roman Catholic church in North America.

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

The semi-reclaimed ruins of this canal were once part of an ambitious plan to reroute the mighty potomac.

Every drop of D.C. tap water flows through this old waterworks.

The only Civil War battle in Washington D.C. took place near this highest natural point in the city.

Once home to seven different roller coasters, Glen Echo has undergone many transformations since its founding in 1891.