The Killing Fields in Phnom Penh are probably the most depressing place to visit in Cambodia. The realisation that mass killing of their own people went on not that long ago. Knowing that it was only 40 odd years ago it gives the place a certain edge.
You can walk around past the mass graves and see bones still sticking out of the ground where recent rain has unearthed up some more bones. Women, children & Men, no-one was discriminated against, they were all there.
The image below is of a collection of skulls that are displayed at the Killing Fields. There are more than 20 levels, each full of skulls.