Inscription: THE GALLOWS. This pole with cables attached to it had been used for the student to conduct their exercise. The Khmer Rouge utilized this place as interrogation room. The interrogators tied both hands of the prisoners to the back by a rope and lift the prisoners upside down. They did like this until the prisoners lost consciousness. Then they dipped the prisoner's head into a jar of smelly, filthy water, which they normally used as fertilizer for the crops in the terrace outside. By doing so, the victims quickly regain consciousness, and that the interrogator could continued their interrogation.
In 1975 the Khmer Rouge turned Tuol Svay Prey High School into a prison and interrogation center known as Security Prison 21. It became the largest detention center in the country, and out of almost 20,000 prisoners detained there only seven survived. When the Vietnamese liberated Phnom Penh in 1979, they turned the prison into a genocide museum.