Richmond, Va. Castle Thunder, Cary Street (U.S. Civil War) Castle Thunder is a former Confederate prison located in Richmond, Virginia, during the American Civil War. Situated on Cary Street, it served as a major prison facility for Union soldiers captured by Confederate forces. The complex consisted of several buildings, including a large stone fortress used as an officers' jail and numerous other structures housing enlisted men. Thousands of prisoners passed through its walls during the war, experiencing harsh conditions and diseases such as smallpox and dysentery. After the war, Castle Thunder was abandoned and later demolished in the 20th century to make way for new construction. Today, little remains of this significant historical site, serving as a poignant reminder of the hardships endured by soldiers during the American Civil War.