The Amazon river is a massive, intricate water system weaving through one of the most vital and complex ecosystems in the world. The Amazon rainforest in South America. It is by far the mightiest river on Earth in terms of volume and width - reaching a span of nearly 30 miles (48 kilometers) in some parts during the rainy season. The river and its basin are home to many unique species of animals, trees and plants. The Amazon river's 4,000 -mile (6,437km) journey begins high in the Andes. These mountains act as a wall blocking the warm, moist air moving in from the east, resulting in heavy persistent rainfall that consistently feeds the Amazon's headwaters. The river then makes its way east through thousands of miles of rainforests and lowlands until it empties into the Atlantic Ocean on the northeastern coast of Brazil. The Amazon river is the second longest river in the world, slightly shorter than the Nile river (4,258 miles or 6,853km.