Middle Rhone Valley, near Tournon-sur-Rhone, France. In this region, the river forms the border between the Ardeche and Drome departments of France. The Rhone is one of the largest rivers in Europe, flowing over 800 kilometres north-to-south from the Swiss Alps to the Mediterranean Sea. This area is about halfway along its course. Fields are either side of the river in an area of lowlands where it has carved a meandering path between low hills.