Thanks! But what do you think is the right answer, wikipedia mentions lots of rivers, do you know which ones actually go through the city? "the Ljubljanica, the Sava, the Gradaščica, the Mali Graben, the Iška and the Iščica Rivers"
Ljubljanica flows through the center of Ljubljana and Sava is on periphery, but not less important. My suggestion is that main answer should be Ljubljanica, and you can put Sava in type-ins. Same like Belgrade, my homecity, lies on Sava-Danube river mouth. You are welcome :)