Phnom Penh is not a very touristy place but it is worth a visit to learn and understand more about Cambodia.

The day I visited the Killing Fields and S21 was definitely the most emotional day while in Cambodia. During Khmer Rouge regime (1975-1979) almost 1.5 million people were killed and buried in the fields. In total almost half of the whole population died as a result of the regime, starvation or diseases during this time. If you wish to find out more, please read http://en.wikipedia.org/wiki/Killing_Fields.

When I arrived to the Killing Fields, it seemed nothing but a quiet green site with singing birds. I got a headset and quietly at my own pace walked around the site. I realised what tragic stories the fields are keeping. It shook me to the core seeing bones and clothes coming up from under the ground... I can't even begin to explain the emotion while there.

Same feeling follows in S21 - a former high school that was used as a Security Prison 21 during Khmer Rouge regime. The cruelty that took place there is shocking... Can still see stains of blood in some of the prison cells... http://en.wikipedia.org/wiki/Tuol_Sleng_Genocide_Museum

While in Phnom Penh, I also visited the beautiful Royal Palace and National Museum.

I think it is important to see these sites just to better understand the local people and the country you are visiting.