Beni (bāˈnē) [key], river, c.1,000 mi (1,600 km) long, rising in the Cordillera Real in Bolivia, flowing NE through the Andean hills. It joins with the Mamoré to form the Madeira River. Steam navigation is possible from December to May between Rurrenabaque, in the Andes, and Esperanza, near the junction with Mamoré.
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