Anavilhanas Archipelago is the largest inland archipelago in the world. There are nearly 350 islands that constitute this archipelago. The water that surrounds Anavilhanas vary a great deal by as much as 15 meter; due to which the channels and sandbars keep on changing and only an experienced guide can navigate through them without getting lost. This archipelago lies within the Anavilhanas Ecological Station which is recognized as an important ecological destination for marine life. Protected species that are found here are several species of freshwater turtle, Amazon pink river dolphin, pirarucu which is the world's largest freshwater fish and many bird species.