S-21 was a secret prison operated by the Pol Pot regime in the capital city of Phnom Penh from mid-1975 through the end of 1978. Individuals accused of treason, along with their families, were brought to S-21 where they were photographed upon arrival. They were tortured until they confessed to whatever crime their captors charged them with, and then executed. The prisoners' photographs and completed confessions formed dossiers that were submitted to Khmer Rouge authorities, so that proof of the elimination of "traitors" was established. Of the 14,200 people imprisoned at S-21, which held between 1,000 and 1,500 at any one time, only 7 are know to have survived. After Phnom Penh was liberated by the Vietnamese Army in 1979, S-21 was transformed into The Tuol Sleng Museum of Genocide.

Alf also has a travelogue of the horrifying museum: "All of these are from the torture chamber run by Pol Pot in Cambodia. It was formerly a high school. I first visited it in 1991 and have a large number of photographs of the place that are no longer on public view. When we went there the place was still mined and we needed an armed guard. We were on our way to North Korea at the time. I will post some of the North Korean photos later...."