If one thing shines through as indicative of the 20th century, sadly it might be genocide. All of our technological advances have lead to the more efficient killing of our fellow man. Estimates range drastically but it is almost universally accepted that over 100 million people died at the hand of genocide in the 20th century.
This picture is from inside the walls of the Tuol Sleng memorial in Phnom Penh where in the 1970′s the Khmer Rouge killed over 1.5 million of its own people. The torture was brutal and they murdered almost indiscriminately.
The warden of this prison, Duch, is currently on trial awaiting his fate. He fled Phnom Penh after the rebellion was suppressed and lived out in the countryside for years. After a conversion to Christianity in the mid 1990′s Duch was placed on trial earlier this year, and has asked to receive the maximum penalty for his crimes against humanity, asking even to be stoned if the court sees it fit.