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

The school tested mustard gas for the U.S. Army during World War I.

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

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

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.

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

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

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

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

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

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

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

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

A fantastic array of trays and cables once whisked books over to the Capitol at 600 feet per minute.

A museum cafe showcases Native American dishes and indigenous ingredients from across the Western Hemisphere.

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

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

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

Home to a vast and influential collection of Shakespeareana.

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

A brass plaque dedicated to a convicted cannibal hangs in the National Press Club, and that's not even the craziest part of the story.

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

Government testing at the asylum briefly explored using marijuana as a "truth serum" on Nazi prisoners of war.

This stunning blue and gold room changed cities twice before becoming part of the Smithsonian.