river in western Africa, rising as the Tienba in the highlands between Odienné and Boundiali, northwestern Côte d'Ivoire, and becoming the Sassandra 36 miles (58 km) east-northeast of Touba at its confluence with the Férédougouba (Bagbé) River from eastern Guinea. It then follows a 400-mile (650-kilometre) south-southeasterly course through Côte d'Ivoire and empties into the Gulf of Guinea at Sassandra, an Atlantic port. Its upper reaches flow through a savanna region and have been panned for diamonds; its lower course marks the eastern boundary of the 1,641-square-mile (4,250-square-kilometre) Taï Reserve (known for pygmy hippopotamuses) and flows through an area noted for timber (sipo and mahogany), coffee, and bananas. Frequent rapids impede the navigability of the river, but small craft can penetrate 50 miles (80 km) upstream.