Mixing of the black water of the Nanay River with the whitewater of the Amazon River. Blackwater rivers originate in the Amazon rainforest and, although silt-free, take on the color of cola from dissolved tannins. Whitewater rivers, such as the Amazon, originate in the Andes mountains and their heavy load of silt gives them an opacity and coffee-with-milk color. The Nanay River joins the Amazon just outside of the port of Iquitos, Peru. Iquitos, 2,200 river miles from the Amazon's mouth, is considered the furthest inland port city in the world. The most famous mixing of white and black water is the junction of the huge Rio Negro with the Amazon at Manaus, Brazil.