Exterior of S-21 prison, photographed on January 8, 1979, by Vietnamese journalist Ho Van Tay. Also known as Tuol Sleng, the prison was formerly a high school before the Khmer Rouge transformed it into a death camp that neighbors described as a place "people entered but never left." Nearly 30,000 people were imprisoned at S-21, and later killed. Photographer Ho Van Tay discovered the prison from its stench of decomposing bodies—from several kimometers away—as he entered Phnom Penh with the invading Vietnamese forces that ousted the barbaric Khmer Rouge. Even Ho Van Tay, a faithful Communist who had travelled extensively behind the Iron Curtain, was shocked to see what Pol Pot had done to Cambodia. Only two days before this photograph was made, the prison operation was in full swing. Photograph: © Ho Van Tay