The Toul Sleng Genocide Museum(សារមន្ទីរឧក្រិដ្ឋកម្មប្រល័យពូជសាសន៍ទួលស្លែង ) is a museum in Phnom Penh,the capital of Cambodia.The site is a formerhigh school which was used as the noturious Security Prison 21(S21) by the Khmer Rouge regime from its rise to power in 1975 to its fall in 1979.Toul Sleng .means"Hill of the poisonous Trees "or" Strychnine Hill"

+Formerly the Chao Ponhea Yat High School,name after a Royal ancestor of King Norodom Sihanouk,the five buildings of the complex were converted in August 1975,four monthe after the Khmer Rouge won the civil war,into a prison and interrogation centre,The Khmer Rouge renamed the complex "Security Prison 21(S21) and xonstruction began to adapt the prison to the inmates: the buildings were enclosed in electrified barbed wire,the classrooms converted onto tiny prison and torture chambers, and all windows were covered with iron bars and barbed wire to prevent escapes.

From 1975 to 1979,an estimated 17,000 people were imrisoned at Toul Sleng(some estimates suggest a number as high as 20,000 although the real number is unknown).At any one time,the prison held between 1,000-1,500 prisoners,The were repeatedly tortured and coercred into naming family members and close associates,who were in turn arrested,tortured and killed.In the early months of S-21's existence,most of the victems were from the previous Lon Nol regime and included soldiers,government officials,as well as academics ,doctors,teacher,students ,factory workers,monks,engineers,etc.Later,the party leadership's paranoia turned on its own ranks and purges throughout the coutry saw thousands of party activists and their familleis brought to Toul Sleng and murdered.Those arrested included some of the highest ranking communist politicains such as Khoy Thoun, Vorn Vet and Hu Nim.Although the official reason for their arrest was "espionage" families were often brought en masse to be interrogated and later murdered at the Choeung Ek extermination center.In 1979,the prison was uncovered by the invading Vietnamese army,in 1980,the prison was reopened by the goverment of the people'sRepublic of Kampuchea as a historical museum memorializing the actions of the Khmer Rouge regime.The museum is open to the public,and receives an average of 500 visitors every day.