Before Metro, Washington had a robust streetcar network—and you see the remains of this infrastructure if you know where to look.

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

Daredevil repair workers can worm their way out the access hatch, loop ropes over the apex and rappel down the monument.

When it comes to handsignals (and colonialism) rock always beats scissors.

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

This forgotten boat elevator was an engineering marvel in its heyday.

The only National Monument ever to go missing for nearly 50 years then resurface in a dump.

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

Before Nixon, "watergate" meant canals.

Architecture lovers won’t stop touching the National Gallery's 19.5 degree marble prow.

A much-maligned monument to teetotalism.

One of the largest artillery pieces in the world sits in a Washington D.C. parking lot.

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

Legend has it that President Grant’s frequent drinking in the lobby gave rise to the term “lobbyist.”

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

A historic ruin just 20 feet away from a busy highway onramp.

This poor little statue is the most vandalized memorial in Washington.

The span is crooked and made from two older recycled bridges.

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

The hidden offices underneath Memorial Bridge have been locked up since 1976.

Perhaps the most scandalous statue of America's first president.

These recently uncovered walls are all that's left of Washington, D.C's first defense contractor.

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

A celebrity from the late Cretaceous period.