The wildlife-rich Río Tambopata is a major tributary of the Río Madre de Dios, joining it at Puerto Maldonado. Boats go up the river, past several good lodges, and into Reserva Nacional Tambopata, an important protected area divided into the reserve itself and the zona de amortiguamiento (buffer zone). The big draw is the birdlife: chattering groups of macaws and parrots gather to feed at clay licks here. Sightings of jaguars on the riverbanks are not unusual, either.
Park entrance fees must be paid at Puerto Maldonado's Sernanp office if you are not on a guided tour, in which case you'll pay at the relevant lodge office. An additional fee is required if you are heading into the reserve proper (such as to the Tambopata Research Center) rather than just the buffer zone.