Argentina is a massive, megadiverse South American nation, hosting one of the greatest ecosystem varieties in the world. This huge ecosystem variety has led to a biological diversity that is among the world's largest. It is divided into seven geographical regions: Northwest, the high Puna with even higher, more rugged topography to the far-west; the arid precordillera, filled with narrow valleys or quebradas to the mid-west; and an extension of the mountainous Yungas jungles to the east. Mesopotamia is a subtropical wedge covering the western Paraná Plateau and neighboring lowlands, and is enclosed by the Paraná and Uruguay rivers. Gran Chaco is a large, subtropical and tropical low-lying, gently sloping alluvial plain between Mesopotamia and the Andes. Sierras Pampeanas are a series of medium-height mountain chains located in the center of the country. Cuyo is a basin and range area in the central Andes piedmont, to the west of Argentina. Pampas is a massive and hugely fertile alluvial plain located in the center-east. Patagonia is a large southern plateau consisting mostly of arid, rocky steppes to the east, with moist, cold grasslands to the south, and dense subantarctic forests to the west. (Wikipedia)