In 1975, Tuol Svay Prey High School became Pol Pot's largest interrogation centre, under the name of S-21 (Security Prison 21). Under the command of Douch (condemned to a life sentence in 2012), thousands of inmates were tortured and killed here. These crimes lasted four years until January 7, 1979, date of the camp's liberation by the Vietnamese army. A tragic and indefensible page of history that should not be forgotten.