During the renovation of the Smithsonian Castle in Washington, D.C., a hidden chamber was discovered beneath Jefferson Drive. The round brick cistern, built in 1847 for rainwater storage, remained sealed for over 120 years. The 30-foot deep chamber was found by construction crews, offering a glimpse into the museum’s past. While myths of underground Smithsonian archives persist, the real find was the empty cistern. The ongoing Castle Revitalization Project has brought extensive construction to the iconic building, preserving its historic red stone exterior. This discovery sheds light on the capital’s infrastructure history, though no national treasures or secret symbols were recovered from the chamber.
https://www.smithsonianmag.com/smart-news/workers-uncover-an-underground-chamber-sealed-for-more-than-a-century-near-the-national-mall-180985018/