With Smithsonian Castle renovations underway, a surprising archaeological discovery has just come to light: a sealed chamber under the National Mall. Measuring 9 feet in diameter and 30 feet deep, it was built as a round cistern to collect rainwater. However, the brick-lined cistern was dry upon discovery, having been sealed for over 120 years.
Washington, D.C. has long been rumored to disguise secret tunnels and other mythic structures reminiscent of National Treasure, but as the National Park Service put it, “Sadly, no national treasures or secret symbols were recovered, but the cistern offers a neat glimpse into the museum's and the National Mall's past.”
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- Photo Credit: National Park Service
While we don’t currently know much about the cistern and how it fell into disuse, the discovery came about as part of the Smithsonian Castle Renovation Project, embarked upon in February 2023 and involving updates to the Castle’s windows, roof and utilities systems. (The iconic red stone exterior will remain unchanged.) Located on the National Mall, the Castle was built as the first Smithsonian museum building. It was completed in 1855 and designated a National Historic Landmark in 1965.
While lovers of historical mysteries may have hoped the discovery of the sealed chamber would lead to something more sensational than a cistern, this fun factoid serves as a reminder that history is everywhere—even under our feet!
