1. Amazon

This episode is a pioneering exploration of the latest discoveries concerning the Amazon - by far the greatest river on Earth. It is the river of superlatives, flowing more than 4,000 miles from the Andes to the Atlantic. Its 1,100 tributaries drain the greatest river basin on the planet and along its incredible journey it collects and transports one-fifth of the world's fresh water. Its outflow into the Atlantic Ocean per second is greater than the next six rivers combined. It truly lives up to its mighty reputation.....Due to its enormous size, it still hides secrets - it truly is the mysterious river of myth and legend, and it really does have monsters living in it, like giant electric eels and botos - the world's largest species of river dolphin.