Tuol Sleng was the location where the Democratic Kampuchea (DK) regime more commonly known as the Khmer Rouge (KR) regime, set up a prison to detain individuals accused of apposing Angkor. It was established in 1976.

It was the most secret of prisons for the interrogation and extermination of anti-Angkor agents.

The actual building used to be a high school converted into torture cells.

The victims in the prison came from all walks of life. They were of different Nationalities and included Vietnamese, Laotians, Thai, Indians, Pakistanis, British, Americans, Canadians, New Zealanders and Australians but the vast majority were Cambodians. The civilian workers composed of workers, farmers, engineers, technicians, intellectuals, professors, teachers, students, ministers and diplomats. Whole families including new born babies were taken on mass to be exterminated.