Concierge.com's insider take:
To travel on the Amazon River, first head to Iquitos, where vestiges of 19th- and early 20th-century European rubber boom architecture meet the so-called Venice of the Amazon: the ramshackle suburb of Belen, whose floating market offers everything from piranhas to plantains. Iquitos also serves as the home base for Aqua Expeditions, an operator of luxury cruises in the fabled Pacaya Samiria Reserve and other places.
Another sector of Peru's Amazon basin, Manu National Park, has the greatest biological diversity of any place on the planet. Marquis inhabitants of this vast UNESCO Biosphere Reserve include jaguars, giant river otters, and all manner of parrots and monkeys. However, given the resident ecosystems' inherent fragility—and the critical importance of conservation—the lay visitor has access to only a fraction of the reserve. (Access is restricted even for researchers and NGOs.) That said, Manu Wildlife Center is a great place to observe some of the park's most colorful birds and elusive mammals.
A third stunning swath of the Peruvian Amazon—where travel is considerably easier than in Manu—is the Tambopata National Reserve. Rainforest Expeditions operates three of the best local lodges there. While the facilities are admittedly spare, they place you—and a crack team of biologist guides—in the middle of some of the most surreal wildlife displays in existence, not least the sunrise macaw-fest at the massive clay lick next to the Tambopata Research Center. Much closer to Tambopata's air hub of Puerto Maldonado, Reserva Amazonica is the best local luxury option.—Updated by Abbie Kozolchyk