The Tuol Sleng Genocide Museum
S21 was former Phnum Pénh high school and the Khmer Rouge's version of a concentration camp. The number of survivors can be measured with single digits. To measure the number killed requires 7 digits.
I didn't take many photos here as they would have been too gruesome for consumption.
Prison block B
Pol Pot's minister of Agriculture (and his brother in law) was a prisoner here too. No one was sacred.
Map of Cambodia in human remains