The Tuol-Sleng Genocide Museum is the former S-21 prison of the Khmer Rouge and serves as a reminder of the crimes committed there. The building complex is an old school in the city, including the Tuol Svay Prey Gymnasium, located on 103rd Street, used by the Khmer Rouge as a prison with systematic torture of the inmates after the conquest of Phnom Penh.
To this end, the four buildings of the school were surrounded by an electric fence and the classrooms converted into prison cells and torture chambers. Barbed wire braid in front of the exterior of the individual buildings should prevent desperate prisoners from committing suicide. Between 1975 and 1979, between 14,000 and 20,000 people from all parts of Cambodia were imprisoned, including those of the Khmer Rouge, who were considered traitors in the eyes of the leadership of the Khmer Rouge. About 1,720 people were working for the torture center.
The museum was set up after the invasion of the Vietnamese forces in 1979. Duch himself could flee after he had ordered the liquidation of all inmates. He had no longer enough time to destroy the comprehensive documentation of the atrocities committed there.