The Bolivian plateau has an average altitude of 3 700 meters and is surrounded by the Cordillera Occidental, along the border with Chile, where is the highest mountain in the country, the Nevado de Sajama that reaches 6 542 metres, and the Cordillera Oriental, which in the Cordillera Real exceeds 6000 metres, with the peaks of Illampu (6 485 meters) and Illimani (6 322 metres). The plateau is dotted with lake basins including lakes Poopó (2 800 sq km) and Titicaca (8 300 sq km), the latter divided between Bolivia and Peru, at an altitude of 3 810 metres, is the largest lake in South America and the highest navigable lake in the world. In the south-west is also of the Salar de Uyuni, a huge desert of salt (12 000 square kilometres), located at 3 650 meters od altitude, which represents the largest expanse of the salty in the world. The three fifths of the Bolivian territory is made up of the lowlands of the Amazon forest and Chaco, in these areas are the main rivers of the country, the Beni and the Mamoré, tributaries of the Amazon through the Madeira, and the Pilcomayo, tributary of the Paraná through the river Paraguay. Bolivia is, by income per capita, one of the poorest countries in South America, this figure contrasts with the great wealth of natural resources present on its territory, activity of mining is the main resource of Bolivia, are extracted in large quantities tin (Bolivia is one of the main world producers), gold, silver, lead, copper, bismuth, zinc, tungsten, antimony, natural gas and oil. For the domestic market are also important the breeding of livestock (cattle, pigs, sheep, poultry, lamas and alpacas) and agriculture (barley, oats, potatoes, corn, rice, wheat, coffee, cassava, oranges, bananas, cotton ). But the most widespread cultivation is coca that is widely consumed by Indios, which represents the main source of income for most of the peasant population. Considerable the tourist potential of the country, thanks to the beautiful natural landscapes of Andean highlands, interesting colonial cities, and still intact culture of indigenous people.