Мараньон
The source of the Marañón River had been considered as the main source of the Amazon River for a number of centuries. This source was determined by a Czech Jesuit priest named Father Samuel Fritz who sailed the Amazon River from its mouth upstream and drew the first map of the Amazon River basin. Besides this he published experiences from his life among the Indigenous people living in this area. His map from 1707 shows the Marañón River as larger than the Ucayali River, and thus the main source of the Amazon River. Fritz believed that the Marañón contributed the most water of all the Amazon's tributaries, making it the most important headstream. He pinpointed the source of the Marañón River as Lake Lauricocha in the high Western Andes. This lake () is located at an altitude of . The Lauricocha River issuing from Lake Lauricocha joins the Nupe River a few miles downstream and is afterwards known as the Marañón River.