River, southern Peru.
Arising in the Andes Mountains in Peru, it is the most distant source of the Amazon River . It flows northwest to join the Urubamba River and form the Ucayali River . For most of its 430-mi (700-km) length, it flows through narrow canyons, and its course is interrupted by falls and rapids. Short stretches of its lower course are also called the Ene River and the Tambo River.