One of the big horror stories of Cambodia is the genocide that occurred not so long ago (1975-1979). The Khmer Rouge (also known as the Communist Party of Kampuchea) tried to reform the country, while killing around 2 million Cambodians in the process.
In Phnom Penh, we visited S21 (the Tuol Sleng Genocide Museum) - a school that was converted to a security prison where Cambodian were tagged, interrogated, and kept, before being executed. We also rented a motorbike to visit the Killing Fields, where large numbers of Cambodians were brought to be executed and buried in mass graves. The 2 genocide sites are now memorials filled with stories, photos, and artist depictions. The Killing Fields also have an audio guide that lead you through the grounds, filling your mind with first-hand accounts and vivid glimpses of the horrors that took place here... not just to soldiers of war, but to millions of innocent villagers including women, children, and even infants. Evidence of bones and clothing lay scattered in the mass graves of the Killing Fields. Each year, the rainy season continues to uncover new artifacts from the massacre, which are carefully collected and stored in the various display cases at the site.
We've been to several genocide museums in our travels now, yet each one continues to leave us astounded at how thin the line is between human decency and ravaging cruelty.