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

The early data processor factory founded in Washington for the 1890 U.S. Census went on to become IBM.

Behind an abandoned storefront is an example of pioneering 1930s gas station architecture.

A muscular Art Deco monument represents the struggle between regulators and unbridled markets.

A surprising, but overlooked example of geology in the middle of the nation’s capital.

Also known as the Founding Church of Scientology.

Helen Keller once broke ground on this historic center for the study of technologies to benefit the hearing impaired.

They sort through millions of dollars worth of diplomatic gifts on behalf of the government.

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

The fountains of the U.S. Navy Memorial are annually salted with water from the Seven Seas as part of a nautical ritual.

An overlooked memorial honoring the local Washington residents who died in World War I.

The first memorial dedicated solely to the Black troops who fought for the Union.

A bas relief commemorates the "Nuns of the Battlefield" who cared for soldiers on both sides of the conflict.

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

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

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

100 years later, they're still down there.

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

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

Art deco landmark on the outskirts of Washington, D.C.

Before Nixon, "watergate" meant canals.

Washington's top-secret Cold War-era doomsday communications tower is located in a small neighborhood park.

There’s a special club house at the top for the bell ringers.

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