One of the most pristine areas of Peru’s northern Amazon is the Reserva Nacional Pacaya Samiria, an immense wedge of flooded rainforest between the Ucayali and Marañón Rivers. At just over two million hectares, it is still Peru’s largest nature reserve. Its vast network of lakes, lagoons, swamps, and wetlands harbors many endangered animals, with big chances for spotting wildlife rivaling that in Parque Nacional Manu , though there are no lodges in the reserve.
Commonly seen animals in the reserve include huge Amazon manatees, tapirs, gray and pink river dolphins, black and white caimans, giant otters, at least 12 types of monkeys, the paiche fish, and hundreds of aquatic birds. The best times to visit the park are the low-water months July–December, when animals can often be spotted on the riverbanks.
The Reserva Nacional Pacaya Samiria began in the 1940s in an effort to save the endangered paiche. After biologists realized its world-class biodiversity, the present reserve was officially established by the Peruvian government in 1972. More than 30,000 colonists and indigenous inhabitants live inside the reserve, including Cocama, Huitoto, Bora, and Yagua Indians.
Visitors to Pacaya Samiria require a guide, a US$33 entrance fee, and at least five days, whether you motor the 300 kilometers upriver from Iquitos  (15–18 hours) or downriver from Yurimaguas  (10 hours). Because there are no lodges in the reserve itself, options range from deluxe cruises to rustic camping trips.
Trips usually travel up the Río Ucayali to the town of Requena, and then enter the heart of the reserve through the Canal de Puinahua and the Río Pacaya. Generally speaking this southern side of the reserve has more wildlife than the northern area along the Río Samiria.
A fast access point for the reserve is Yurimaguas , which lies two hours from Tarapoto . Cargo boats  that leave here most afternoons chug down the northern border of the park for nearly two days. The fringes of the park, however, have been heavily impacted by colonists, and the more pristine areas can now only be reached by a two- to three-day canoe journey inside the reserve.
In the middle of the first night after leaving Yurimaguas , cargo boats  stop in the small village of Lagunas. From here it is possible to contract a local guide and a canoe for about US$30 per day, though there are no guarantees on the quality of service.
A surer bet is to set up a guide and transport in Tarapoto  through either Puerto Palmeras (Carretera Marginal Sur Km 3, tel. 042/52-3978, cta [at] puertopalmeras [dot] com, www.puertopalmeras.com ) or adventure guide César Reategui (Lamas 261, tel. 042/52-3899, lapatarashca [at] hotmail [dot] com, www.lapatarashca.com ).
From Lagunas, a half-hour mototaxi ride will take you to the headwaters of the Río Samiria. From here, it is a three-day paddle to Laguna Pastococha, a huge oxbow lake teeming with wildlife. Fewer tourists enter the park via this route, so this is more of a wilderness experience. The farther you go, the more you are likely to see.
Camping and canoeing through the reserve is an amazing experience with the right equipment and a good operator. When combined with a stay at a community-based lodge, it is one of the best ways to understand the rhythms of life in a flooded forest.