Doubs, river, c.270 mi (435 km) long, rising in the Jura Mts., E France, and flowing northeast, forming part of the French-Swiss border, then looping into W Switzerland before turning back into France where it meanders southwest to empty into the Saône River. Lake of Brenets, a natural widening in the river, is a tourist center; at the northern end of the lake the river drops 88 ft (27 m). The Doubs is heavily canalized and passes through several industrial cities including Montbéliard and Besançon.