Visiting the S21 prison, converted from a former schoolhouse, was a sobering way to spend New Year’s Day. Over four years three million people were killed and buried in mass graves spread over 143 killing fields. This gallery shows the mass graves at the main killing field in Phnom Penh. The two men in the photos told stories of how they were held in the S21 prison and targeted for killing but managed to avoid it. One is pointing to a picture of himself as a seven year old boy who hid under a massive pile of clothes. The other, pointing to blackboard, was a math teacher who convinced his captors he could not read and write and thus escaped the fate of other intelligentsia.