The Tuol Sleng Genocide Museum is a museum in Phnom Penh, the capital of Cambodia, chronicling the Cambodian genocide. The site is a former secondary school which was used as Security Prison 21 (S-21) by the Khmer Rouge regime from its rise to power in 1975 to its fall in 1979. From 1976 to 1979, an estimated 20,000 people were imprisoned at Tuol Sleng (the real number is unknown). Tuol Sleng (Khmer: ទួលស្លែង Khmer pronunciation:[tuəl slaeŋ]) means "Hill of the Poisonous Trees" or "Strychnine Hill". Tuol Sleng was just one of at least 150 torture and execution centers established by the Khmer Rouge, though other sources put the figure at 196 prison centers. On July 26, 2010, the Extraordinary Chambers in the Courts of Cambodia convicted the chief of Tuol Sleng Prison, Kaing kek Iew, (alias Duch) for crimes against humanity and grave breaches of the 1949 Geneva Conventions and sentenced him to life imprisonment.