For all of it's grim appearance and history, this is still one of the most compelling things to do whilst visiting Phnom Penh. Set in an old school building this museum was the actual site of a notorious secret prison and torture centre. Many died here, everyone here was tortured and thousands were taken from here to kling fields which can also be visited separately.

You will probably already know that the barbaric instruments of torture, the pens and cells with stained floors and the very graphic photographs and stories, combine to make this a powerful history lesson in human brutality. If you bring younger children you might get plenty of difficult questions and it could be impossible to shield them from the graphic photos of dead victims and paintings of torture in progress.

I would certainly recommend opting for the audio tour as there isn't a huge amount of written display material and some of the areas will look repetitive without the additional explanation. You also get a useful amount of background context as well as some first hand accounts from survivors.

As you move between the four main buildings there is ample opportunity to take a break outside or just listen to the audio without having to look at the displays. The audio lets you repeat or move ahead at your own pace and it is clear and well read.

Towards the conclusion of the tour there is material on the audio that brings you up to speed on the present day genocide and war crimes trials of some of the Khmer Rouge leadership. Shockingly, this is still going on today, has cost hundreds of millions of dollars and only prosecuted about 3 people.

More poignantly, as you leave, there is a chance to meet two of the survivors, both of whom have books to sell about their time in S 21 prison. It's a powerful visit if you take the time to absorb the stories and one that will stay with you longer after your travels are over.