Formerly the Chao Ponhea Yat High School now the site of the Tuol Sleng Genocide museum. The place was transformed into Security Prison by the Khmer Rouge regime in 1975 ab stayed that way until 1979 when the regime lost power.

As many as 17,000 prisoners are said to have been held there. The captives were repeatedly tortured into giving up the names of their friends and family to the regime who were in turn tortured and killed.