I visited S-21 prison as part of my travels in Cambodia - the former school, turned torture centre, used by the Khmer Rouge in suburban Phnom Penh. Selecting an image that goes even part way to capturing the cruelty that was inflicted here, is almost impossible, but I've chosen to show the barbed wire that was outside the cells. It was designed to both keep people in and to stop them throwing themselves off of the balcony & committing suicide.
A deeply moving place.