There's one reason why you need to put an Amazon River cruise at the top of your travel wish list: the region's amazing biodiversity. The Amazon, the world's second-longest river, cuts a path across the continent of South America as it makes it way through Brazil, Columbia and Peru. More than a third of the world's animal species live in this vast river basin's rainforest. A cruise along this mighty river will introduce you to squirrel-size tamarin monkeys, three-toed sloths, monk saki monkeys, scarlet macaws, Amazon River dolphins, Amazonian manatees, giant otters, anacondas, caimans, bull sharks, piranhas, electric eels, jaguars, and much more. And if wildlife encounters aren't enough, you'll also visit villages deep in the heart of the forest where few outsiders venture.