The Tuol Sleng Genocide Museum or simply Tuol Sleng is a museum chronicling the Cambodian genocide.The Tuol Sleng Genocide Museum is a memorial site located in the S-21 prison and torture center used by the Khmer Rouge regime that ruled Cambodia between 1975 and 1979. The Museum bears witness to this tragic period in Cambodian history in order to encourage its visitors to be messengers of peace.