The Rhone Tributary is a river in Europe that flows through France, Switzerland, and Germany. Two of its main tributaries are the Isère and the Saône, both of which are five-letter words. The Isère is a river in southeastern France that rises in the Alps and flows into the Rhone near Valence. The Saône is a river in eastern France that rises in the Vosges Mountains and flows into the Rhone near Lyon.