In short
Phnom Penh is built where the Mekong, the Tonlé Sap and the Bassac meet. The Royal Palace and the Silver Pagoda line the river; the central market, a 1937 Art Deco dome, is the city's landmark.
The city carries the memory of the Khmer Rouge regime. The Tuol Sleng museum and the killing fields at Choeung Ek can be visited, and they are gruelling visits.
What it really costs
Phnom Penh is one of the cheapest capitals in South-East Asia, with a large expatriate community and a decent coworking offer.
Prices are shown in dollars, cash machines dispense dollars, and change under a dollar comes in riel. Notes must be in good condition: a torn dollar is refused.
What nobody tells you
Tuol Sleng and Choeung Ek are done on the same day and nothing else: chaining them with anything more makes no sense. Many visitors come out with no appetite for whatever came next.
Traffic is heavy and snatch thefts from motorbikes are frequent along the riverside and around the Russian market. Bag on the pavement side, phone out of sight.
The rainy season reverses the flow of the Tonlé Sap and swells the lake. It is a phenomenon unique in the world, and it governs the life of the whole country.