The Phnom Penh Prison Museum is located in the south of Phnom Penh, at the junction of 113 Street and 350 Street. Before 1975, it was a middle school. After Khmer Rouge occupied Phnom Penh, it was transformed into S-21 (Security Office 21) prison and interrogation office. At that time, the prisoners were brought here for interrogation or extorting confessions by torture until they were taken to Choeung EK killing ground for execution. More than 17,000 people were imprisoned here, and fewer than 12 survived. Now it is open to the public as a museum, which displays various torture tools, photographs and literature and historical materials. It is also a kind of evidence to reveal the crazy politics of Khmer Rouge. It seems that we need to buy tickets here. It costs two dollars, but when I went in, no one asked us to buy tickets. Maybe it was because there was a group of Western tourists coming in at that time. From the entrance, the first thing you can see is these pictures. The tombs should be arranged on the ground. The red monument is only an archival monument of the Prison Museum set up by the Cambodian Ministry of Culture and Art. It has Cambodia and English on it.