Except for the mountainous western area, Argentina is for the most part a lowland country. It is divided into four topographical regions: the Andean region, Patagonia, the subtropical plain of the north, and the pampas. The Andean region, almost 30% of the country, runs from the high plateau of the Bolivian border southward into western Argentina. Patagonia comprises all the area from the Río Negro to the southern extremity of the continent, or about 777,000 sq km (300,000 sq mi). Rising from a narrow coastal plain, it extends westward in a series of plateaus. In most places, the altitude range is 90–490 m (300–1,600 ft), although it may rise to 1,500 m (5,000 ft). Patagonia is a semiarid, sparsely populated region. It includes the barren island of Tierra del Fuego, part of which belongs to Chile. A portion of the Gran Chaco, covering the area between the Andean piedmont and the Paraná River, consists of an immense lowland plain, rain forests, and swampland, little of which is habitable. The most characteristic feature of Argentine topography, however, is the huge expanse of lush, well-watered level plains known as the pampas.
Stretching from the east coast estuary, Río de la Plata, the pampas spread in a semicircle from the Buenos Aires area to the foothills of the Andes, to the Chaco, and to Patagonia, forming the heartland of Argentina, the source of its greatest wealth, and the home of 80% of its people.
The major Argentine rivers, which originate in the Andean west or the forested north, flow eastward into the Atlantic Ocean. The Paraná, Uruguay, Paraguay, and Alto Paraná rivers all flow into the Río de la Plata, which reaches a maximum width at its mouth of 222 km (138 mi), between Uruguay and Argentina. The highest peaks in Argentina are Mt. Aconcagua (6,960 m/22,835 ft), also the highest mountain in South America; and Mt. Tupungato (6,800 m/22,310 ft). There is a region of snow-fed lakes in the foothills of the Andes in western Patagonia. Many small lakes, some of which are brackish, are found in the Buenos Aires, La Pampa, and Córdoba provinces.