Although not quite the longest river, it is arguably the largest river in the world, as it is several miles wide in many places. It is home to more than 300 species of mammals, and thousands of species of fish, including more than 30 different types of piranha. The Amazon is well known for its rain forest, and has many thousands of trees and plants.
Several river cruise operators offer nice itineraries along the Amazon river, including Avalon Waterways, Cosmos Tours & Cruises,
Titan Travel, and Travelsphere, but some ocean cruise lines offer the Amazon in their itineraries, including Cruise & Maritime Voyages and Fred Olsen Cruise Lines.
(page updated July 2015)