The Marañón River (Spanish: Río Marañón, IPA: [ˈri.o maɾaˈɲon]) rises about 160 km to the northeast of Lima, Peru, flows through a deeply-eroded Andean valley in a northwesterly direction, along the eastern base of the Cordillera of the Andes, as far as 5 degrees 36' southern latitude; then it makes a great bend to the northeast, and cuts through the inland Andes, until at the Pongo de Manseriche it flows through the plains. After its confluence with Río Ucayali, the Marañón is given the name of the Amazon River.
Barred by reefs, and full of rapids and impetuous currents, the Marañón has never become a commercial avenue. At the point where it makes its great bend the river meets the Chinchipe, which originates in southern Ecuador. Just downriver from this, the mountains close in on either side of the Marañón, forming narrow gorges or ping-pongs for a length of 56 km (35 miles), where, besides numerous whirlpools, there are no less than 35 rapids, the series concluding with three cataracts just before reaching the river Imasa or Chunchunga, near the mouth of which Charles Marie de La Condamine embarked in the 18th century to descend the Amazon. In this region the general level of the country begins to decrease in elevation, with only a few mountain spurs, which from time to time push as far as the river and form small-scale ping-pongs. The Aguaruna people live on the river in this area.
The final ping-pong on the Marañón, the Pongo de Manseriche, is 5 km (3 miles) long, just below the mouth of the Rio Santiago, and between it and the old abandoned missionary station of Borja. According to Captain Carbajal, who descended the Pongo de Manseriche in the little steamer "Napo," in 1868, it is a vast rent in the Andes about 600 m (2000 ft) deep, narrowing in places to a width of only 30 m (100 ft), the precipices "seeming to close in at the top." Through this canyon the Marañón leaps along, at times, at the rate of 20 km/h (12 miles an hour).
After passing the Pongo de Huaracayo (or Guaracayo), the cerros, or hills, gradually disappear, and for a distance of about 30 km (20 miles) the river is full of islands, and there is nothing visible from its low banks but an immense forest-covered plain known as the selva baja ("low jungle") or Peruvian Amazonia, home to indigenous peoples such as the Urarina of the Chambira Basin, the Candoshi, and the Cocama-Cocamilla peoples. The Marañón river serves also as a frame for one of the most important novels of the Peruvian writer Ciro Alegría: La serpiente de oro (1935). , 
Marañon River, seen from Cochapata in Peru
Urarina shaman, 1988
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