Geography of South America world by drainage area—the Amazon River and the more southerly Paraná River. The other major river of this central lowland is the Orinoco River, which has a natural channel linking it with the Amazon. Most of this central lowland is sparsely populated because the soils are heavily leached, but in the south is the very fertile pampas of Argentina—one of the world's major food-producing regions where wheat and beef cattle are pre-eminent. The natural vegetation of the northern lowlands are either savanna in the northern "llanos" and southern "campos", or tropical rainforest throughout most of the Amazon basin. Efforts to
Kilometre per square kilometre For cities, most cities are rounded by a motorway ring, so the density metric is dependent on the size of the city: EU-15 had 48.3 km of railways per 1 000 square kilometres in 2000), more than in the United States (30.6 km/1 000 km2 in 1999, including Alaska and Hawaii and inland waters) but less than in Japan (53.5 km/ 1000km2 in 1999). For rail networkds, in Europe, the highest network density can be found in the Czech Republic, Belgium, Luxembourg and Germany (above 100 km/1 000 km²), followed by the Netherlands, Hungary, Austria, Slovakia, the United Kingdom and