Tuol Sleng Genocide Museum

The most notorious of the 189 known interrogation centers in Cambodia was S-21, housed in a former school and now called Tuol Sleng for the hill on which it stands. Between 14,000 and 17,000 prisoners were detained, tortured there, often in primitive brick cells built in former classrooms.

Choeung Ek Genocidal Center

9 miles away south of Phnom Penh. The infamous killing fields have a bloody history. Once an orchard and a Chinese cemetery, the Khmer Rouge, led by Pol Pot, turned the place into what became known as the killing fields, where they executed around 20.000 victim. Over three years, they massacred and buried 2.5 million people.