Argentine "Mesopotamia" is a unique region, enclosed between the rivers Parana to the west and the Uruguay to the east. It comprises three provinces: Misiones, with its falls and Jesuit ruins; Corrientes, with its marshlands; and Entre Rios, with its low hills and its delta.

The biodiversity of the marshes and lagoons of Ibera to the north of the Province of Corrientes make it one of the most remarkable ecosystems in Argentina.

To preserve this and its great variety of species of flora and fauna, Ibera Nature Reserve was created in 1983, comprising over a million hectares, including a complex network of shallows, marshes, lagoons, natural dykes and reservoirs and water courses, all originating from rainfall. This was formerly the bed of the river Parana. Ibera Reserve, (meaning "brilliant waters" in the Guarani language), is approximately 250 kilometers from north-east to south-west, with a width of 150 kilometers. The huge mass of vegetation has an immense water absorption capacity, retaining between 1,200 and 1,500 millimeters of rainfall a year.

A quarter of the rain that falls drains out through the river Corrientes, the only natural outlet from the system, into the river Parana. The rest mostly evaporates due to the extensive surface area and its shallowness, or is metabolized by the vegetation.

The shallows - some 700,000 hectares - are formed by the accumulation of rainwater in depressions in the land during periods of abundant rainfall.

The more than 50,000 hectares of marshlands consist of large amounts of static water, with a depth of up to three meters, covered by a blanket of water plants that float or rise from the bottom. There are also water hyacinth beds, with their floating formations hiding the surface of the water, formed by breakoffs from the banks of the rivers and lagoons. The lagoons - more than 30,000 hectares - cover a quarter of the surface of the reserve showing well-defined shorelines, frequently formed by dykes.

These dykes grow out of the water hyacinth beds, which receive wind-deposited earth or waterborne silt, enabling various species of plants, including even some trees like the ceibo, laurel and curupi, to take root on them. The flora is very varied. On the surface of the water can be seen irupes or water-lilies, water hyacinths, lentils, repollitos, calla lilies, and small ferns; on the dykes and reed-beds, achira, weeds and trees such as laurels, Phyllanthus and large totora reeds. Ombus can be seen on the islands, and jacaranda, lapacho, ceibo, willow, curupi, timbo, guayabi and urunday trees on the banks. The most common palmtrees are the yatay, pindo and caranda.

There is also a wealth of fauna, particularly two species of caiman; the capybara, the largest rodent in the world; marsh deer, the largest in South America; neotropical otter; black howler monkeys; gray brocket deer; wildcat, and the maned wolf or aguara-guazu. The birds deserve a chapter of their own. Hundreds of them, of the most varied colors, can be seen and heard; from the largest, the greater rhea or ñandu, a running bird similar to the ostrich but smaller; different types of herons, the maguari stork, various species of eagles, snipes, woodpeckers, kingfishers, humming birds, magpie tanagers, thrushes and a wide variety of ducks and native birds with indigenous names.

Snakes and amphibians, of course, can also be found.

120 kilometers from the city of Mercedes, Corrientes, and beside the reserve is the Ibera Interpretation Center with an exhibition with graphic material explaining the region's history, geography, fauna, flora and other aspects. Study trails leave from there through the bush and around the lagoon to observe the biological diversity of its flora and fauna. Water trips can also be made with local guides to see the water birds and plants and to be able to walk on the dykes. Other possible activities are horseback riding, photo safaris and fly fishing. Crossing the lagoon by the causeway and the bridge, Colonia Carlos Pellegrini can be reached, a town of less than 1,000 inhabitants. More guided tours can be made from there and the tourist can stay in typical cabins.