Found just below Smithsonian Castle, the chamber appears to be a 19th-century cistern meant to collect rainwater that had been forgotten for more than a century.
National Parks ServiceInside the 19th-century cistern found beneath Smithsonian Castle.
In a statement reminiscent of The Da Vinci Code or National Treasure, the National Park Service announced this week that a “secret chamber” had been discovered beneath the National Mall in Washington, D.C. However, while the chamber is an interesting part of D.C. history, it’s not a secret tunnel with connections to the Freemasons or anything of the sort.
Instead, the chamber was constructed more than 175 years ago as a cistern. While this may be disappointing to some, others remain fascinated by the cistern and its role in the early infrastructure of the nation’s capital.
The Newly-Uncovered Chamber Beneath The National Mall In Washington, D.C.
National Park ServiceFound during the Smithsonian Castle Revitalization project, this cistern marks an “unanticipated archaeological discovery.”
According to a statement from the National Park Service, the “secret chamber” was discovered last month as part of the Smithsonian Castle Revitalization project, which began back in February 2023.
“Is that a secret chamber? Last month, there was an unanticipated archeological discovery under the National Mall,” the National Park Service wrote on X. “While working on the utilities under Jefferson Drive, workers opened up a large brick-lined cistern.”
Based on building reports for Smithsonian Castle, experts believe that the cistern was built in 1847. It’s nine feet in diameter and 30 feet deep. Though the cistern was originally designed as part of a drainage system to collect rainwater, it was sealed and has remained empty for more than 120 years.
National Parks ServiceThe side of the cistern, which was likely first constructed in 1847.
“Sadly, no national treasures or secret symbols were recovered,” the National Park Service wrote, “but the cistern offers a neat glimpse into the museum’s and the National Mall’s past.”
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The Long And Storied History Of The Smithsonian Institution
Public DomainSmithsonian Castle, as seen circa 1849, right around the time of the newly-found cistern’s construction.
Construction of the Smithsonian Institution Building, known as “The Castle,” began in 1847, more than a decade after the funds for the institution were bequeathed by an Englishman named James Smithson. He ordered that his his estate — half a million dollars, or around $14 million today — be used to establish “at Washington, under the name of the Smithsonian Institution, an establishment for the increase and diffusion of knowledge.”
According to Smithsonian, the building itself has long been the subject of eerie rumors about ghosts and secret passageways. The institution denies that there are ghosts — though Smithsonian’s crypt is located on the first floor of Smithsonian Castle — but acknowledges that there are tunnels.
Wikimedia CommonsThe Smithsonian Institution denies that there are ghosts or secret tunnels on its grounds, but it is home to the crypt of its benefactor, Englishman James Smithsonian.
Like the recently discovered cistern, however, these tunnels serve practical purposes. A number of underground passageways open to the staff connect the Freer Gallery, the Sackler Gallery, Smithsonian Castle, the National Museum of African Art, and the Arts and Industries Building. There’s also a tunnel that links Smithsonian Castle with the National Museum of Natural History, but it’s apparently cramped and home to “rats and roaches.”
Though conspiracy theorists may be disappointed that the drainage cistern is just, well, a drainage cistern, it is a fascinating and unexpected find. Sealed for more than a century, this “secret” chamber played a role in the original construction of Smithsonian Castle itself. It’s a window back into the 19th century, and to a time when a wealthy Englishman decided to commit his fortune to the spread of knowledge in a move that continues to benefit the American people to this day.
After reading about the “secret chamber” discovered under the National Mall, enjoy some other posts about Washington, D.C.’s history, like the overlooked story of Frank Wills, the security guard who discovered the Watergate burglars. Then, look through these inspiring photos from the 1963 March on Washington.
