Prison Museum Introduction: TuolSlengMuseum, also called S-21 Prison, is located in the south of the city. It was originally a high school and was used as a concentration camp for prisoners during the Bob period. More than 17,000 intellectuals, civilians, women and children were imprisoned here, and countless people were tortured to death every day. Until the Hengshan Lim regime invaded Phnom Penh in 1979, only 14 corpses and 7 survivors were left in this concentration camp. The torture instruments and descriptions on display in the museum are horrifying.