The large port city of Belem (and capital of Para state) is a good base for half-day river cruises to get a taste of the jungle. (These short cruises are really intended for people who aren't headed farther up the Amazon on longer cruises.)
Belem, which is 1,520 mi/2,445 km northwest of Rio de Janeiro, is a lovely colonial city founded in 1616 that offers enough to justify a two-day stay: the 18th-century Basilica de Nossa Senhora de Nazare; the Emilio Goeldi Museum, including a zoo, botanica...