S21 Prison, also known as the Tuol Sleng Genocide Museum, is a former high school in Phnom Penh, Cambodia, that was converted into a prison and interrogation center during the Khmer Rouge regime from 1975 to 1979. It is infamous for the torture and execution of thousands of political prisoners, with only a handful surviving. The site now serves as a memorial to the victims of the genocide. Today, S21 Prison is a museum that educates visitors about the atrocities committed during this dark period in Cambodian history. It features photographs, personal stories, and artifacts that illustrate the suffering endured by the prisoners, aiming to promote awareness and prevent future atrocities.