The city of Phnom Penh is not what would be called a perfect holiday loacation but I would suggest to spend a couple of days here and explore the recent history of Cambodia. Most routes through Cambodia go through PP anyway.
We saw the Toul Sleng Museum and the Killing Fields. The two sites are examples of the cruelty that the cambodian people had to face during the Khmer rouge regime in the seventies. We did both without a tour but with the Audio Guide. Take the audio tour otherwise you will not comprehend the meaning of either one of these sites and might leave disappointed. We did the Museum in the afternoon and the fields the next day in the morning. If you are in a hurry it is possible to do it in one day but since it is exhausting and depressing I would recommend to split it up.
The russian market is a fun place to see and it has good lunch options. We ate some fried noodles -delicious-. Street 240 has some more expensive shopping options but most of the buisnesses are fair trade/support locals. The riverside was not our favourite since we have seen prettier riversides but while you are there you could stroll around for a bit. The night market is okay but nothing like the Thai night markets we have seen.
We did not have the feeling that PP is more dangerous than other big cities we had been to but we tried to avoid walking long distances at night and tried to keep our phones inside the bag rather than in our hands. Please do not judge us on not visiting the Palace and the National Museum. We have still some other places to see Museums and felt quite exhausted. Instead we did some planning, blogging, packing and played some board games at the hostel.