The Amazonas is the greatest river of South America and the largest drainage system in the world in terms of the volume of its flow and the area of its basin. The total length of the river—measured from the headwaters of the Ucayali-Apurímac river system in Peru—is about 4,000 miles (6,400 kilometres).

Iquitos, city, northeastern Peru, capital of Loreto Department. It is a port on the Amazon River, approximately 100 km (about 60 mi) from the point at which the Marañón River unites with the Ucayali River to form the mainstream of the Amazon.