The largest river archipelago in the world, Anavilhanas, in Amazonas state, is made up of 400 islands and hundreds of lakes, rivers, swamps and sandbanks, all rich in animal and plant life. It is situated on the river Negro and is a paradise for biologists and ecologists. The archipelago is protected by federal law, which established the Anavilhanas Ecological Station, with an area of 350,000 hectares. The period from November to April marks high water on the river Negro, and half the islands are submerged, forcing the animals to take refuge on higher ground. When the waters retreat, the islands expose to view beaches and 90 kilometers of canals, which intersect the whole region. Anavilhanas is near the Jau National Park, the largest forest reserve in South America at 2.27 million hectares, also on the river Negro.