I am relatively new to ArcGIS so please bear with me!! I am looking to find the least cost path between a number of points in a landscape (eastern Sicily) that avoids rivers (obviously a Roman cart would not plough through a river). I have DEMs for the elevation and ran the analysis for the slope, and I had a shapefile for the rivers which I used to also create a feature; I've used conversion tools with this to create a raster for the rivers too. I'm just not sure where to go from here! Any help would really be appreciated; I'm sure this is a really simple solution but I only just started using this program recently. (Not sure if it's relevant but I'm using ArcGIS 10 on Windows 7).

Edit: I do know how to use the cost distance, back link, and cost past tools to find the least cost path; my problem is getting the rivers incorporated into this.