This hard-to-reach park comprises a vast expanse of wilderness between the Marañón and Ucayali rivers, which flow together to form the Amazon. The reserve is Peru's largest, encompassing more than 20,000 square km (7,722 square mi)—which makes it about the size of El Salvador. The landscape is diverse, comprising a patchwork of seasonally flooded forests, oxbow lakes, black-water rivers, aguaje palm swamps, and vast expanses of lowland rain forest. So are the
animals who inhabit it, including pink river dolphins, black caimans, more than a dozen kinds of monkeys, and more than 500 bird species. As with many South American reserves, there are people living in Pacaya Samiria, around 40,000 according to recent estimates. Park rangers try to balance the needs of these local communities with efforts to protect the environment, and request a minimal S/120 entrance fee to help pay for that work. The park can only be reached by boat, but it's northern end lies quite close to the town of Nauta, 100 km (60 mi) south of Iquitos by road.