The Khmer Rouge took Phnom Penh on 17 April 1975 and declared Year Zero. Cities were emptied, money and schools abolished, religion banned, and the population sent to agricultural collectives. Between 1.5 and 2 million people, out of roughly eight million, died of execution, starvation, forced labour and untreated disease in three years and eight months. The regime fell when Vietnam invaded in January 1979.
Tuol Sleng
A secondary school in Phnom Penh became Security Prison 21, where at least 12,000 and possibly 20,000 people were interrogated, tortured and sent to be killed. Twelve are known to have survived. The classrooms are preserved with their iron beds and their photographs: the regime documented every prisoner on arrival, and the walls of mugshots are what most visitors remember. The audio guide is excellent and should be used. Two survivors, Chum Mey and Bou Meng, have often been present at the entrance.
Choeung Ek
Fifteen kilometres out of the city, one of some 300 killing fields, where prisoners from S-21 were taken. Nearly 9000 bodies have been exhumed from the pits; bone and cloth still surface after heavy rain and visitors are asked not to step off the paths. A memorial stupa holds more than 5000 skulls arranged by age and manner of death. The audio guide includes survivor testimony and is the reason to allow two hours.
Visiting
Both sites are open daily and are genuinely distressing. Dress as you would at a funeral, do not take smiling photographs, and do not treat the sites as backdrops; the request is posted and is regularly ignored. Many Cambodian families lost members in these places and staff include their relatives.
The tribunal
A UN-backed court operating from 2006 convicted only three people before closing in 2022: Kaing Guek Eav, the commandant of S-21, and two senior leaders. Pol Pot died in 1998 without trial. The limited number of convictions remains a source of anger.
Afterwards
The country is young: more than half the population was born after 2000. Cambodians talk about this history readily if asked respectfully, and increasingly it is taught in schools, which it was not for decades. Understanding it explains a great deal about the country you are travelling in.