It’s no accident that the Amazon is called mighty. The second-longest river in the world, it flows north and east 4,345 miles from its source high up in the Peruvian Andes, through Peru and Brazil, to its mouth on the Atlantic Ocean. On the way, the Amazon also cuts through a small section of Bolivia. The watershed around it includes the largest tropical rainforest in the world, and a variety of indigenous tribes. Read Article.