To visit the Amazônia National Park, you need to get a permit. One can be obtained here. You need your passport - maybe also a photocopy and some 3x4 cm photos. The permit is free (at last check).
Guide text adapted from the Wikivoyage article "Amazônia National Park" by its contributors, available under CC BY-SA 4.0. Read on Wikivoyage · Contributors · CC BY-SA 4.0
