Phnomn Penh, Cambodia

The thing with the biggest impact the rooms full of photographs of Khmer victims. Cambodia isn’t a large country, yet the Khmer Rouge killed fully two million people in just four years, ending in 1979. Those arrested were imprisoned as part of a "year zero" policy, designed to return Cambodia to an agrarian, anti-intellectual society. Those imprisoned included teachers and academics. Some were imprisoned because they wore spectacles.

The Killing Fields offer a similar perspective. In themselves they are a selection of shallow graves, but the memorial in the middle is a stack of thousands of skulls. The scale of the Khmer Rouge’s terrorisation of its own people is really quite staggering.