Sometimes called the Pantanal of Argentina, Esteros del Ibera is in Corrientes. This is a wonderful place to see all sorts of crazy animals. Kayman (similar to Alligator / Crocodiles), Capybara (worlds largest rodent ~300 lbs), and Anaconda's (big snake) all call this area home. The area is basically a very alkaline shallow water area. There are "islands" in the water area that are just floating plantlife.