Hoa Lo Prison, also known as the Hanoi Hilton, is a historic site that was used during the French colonial period and later during the Vietnam War. The prison was originally built by the French to house political prisoners, but it gained international attention during the Vietnam War when it held American prisoners of war. Today, the prison serves as a museum that documents the harsh conditions and the struggles of the prisoners. Visitors can explore the cells, view exhibitions, and learn about the history of the prison.