[2] The river rises at an altitude of some 700 metres, near the village of La Favière, in the Jurassic limestone of the southern end of the Jura mountains and flows into the Rhône near Saint-Maurice-de-Gourdans,[2] about 40 kilometres upstream of Lyon.

The Jura consists of limestone strata crushed into ridges between the forces of the spreading rift valley of the Saône and the Alps, the latter raised by a collision of the Italian tectonic plate with Europe.

The traditional small products of the region, wood-turning, horn combs and trinkets led to the development of a specialism in the injection moulding, vacuum forming and so on of plastics, beginning with celluloid in 1880.

Some was marketed down river and some converted into charcoal which permitted the rise of water-powered forges working iron from smelters in the Saône valley.

Beavers are also present and construct numerous dams while wild boar and roe deer are found in the woods and forests bordering the stream.

The river's natural surroundings remain relatively wild, and are the subject of an environmental scheme by the name of a SDAGE (Schéma Directeur d’Aménagement et de Gestion des Eaux), set up under a French law.

That involves reconciling the hydro-electric stations with the boating, fishing, swimming and perhaps water extraction in view of the tendency to industrial development on the reclaimed delta land at its confluence with the Rhone at its southern end.