Workers Uncover Underground Chamber Sealed for over a Century Near National Mall

During the renovation of the Smithsonian Castle in Washington, D.C., workers uncovered a hidden underground chamber, a round brick cistern built in 1847 for rainwater storage. This chamber, measuring 9 feet across and 30 feet deep, had been sealed for over 120 years and was discovered while construction crews were working on utilities beneath Jefferson Drive, adjacent to the National Mall. The National Park Service confirmed that the chamber was empty and did not contain any national treasures or secret symbols, but it provides insight into the historical infrastructure of the area. The Castle itself has been closed since February 2023 for extensive renovations, which include restoring its windows, roof, and utility systems, while preserving its historic red stone exterior. The Smithsonian Castle, designed by architect James Renwick Jr., has served as the institution's headquarters since its establishment in 1846 and is listed on the National Register of Historic Places. The discovery of the cistern adds to the narrative of the National Mall's past, amidst various myths about hidden structures beneath the area.

- Workers found a 120-year-old underground cistern during renovations of the Smithsonian Castle.

- The cistern was built in 1847 for rainwater storage and is 30 feet deep.

- The Castle has been closed for renovations since February 2023.

- The renovation project aims to restore the Castle's historic features while preserving its exterior.

- The discovery highlights the historical infrastructure of the National Mall.