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.

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

"Congress may voluntarily remain in session throughout the summer, in order that our Congressmen may be protected from the intolerable discomforts and dangers of the ordinary outdoor weather!”

This stately mansion, built in 1787 by America's first Secretary of the Navy, is rumored to be one of the most haunted buildings in Washington, DC.

Daily lunch spot for many of Washington, D.C.'s cab drivers.

Before founding the American Red Cross, Clara Barton had a tremendous humanitarian impact by locating thousands of missing soldiers.

A tiny monument to the unsuccessful attempt by Thomas Jefferson to place the prime meridian in Washington.

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

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

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

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

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.

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

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

Before Nixon, "watergate" meant canals.

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

This robust fence in front of a historic Georgetown home is likely made from hundreds of recycled Revolutionary War firearms.

This unacceptably tall building was the real reason for Washington, D.C.'s skyscraper ban.

A much-maligned monument to teetotalism.

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

A small triangle of DC grass is the final resting place of one of Sonny and Cher's songs.