Maracaibo, Lake, largest lake of South America, c.5,100 sq mi (13,210 sq km), NW Venezuela, extending c.110 mi (180 km) inland. A strait, 34 mi (55 km) long, connects it with the Gulf of Venezuela. Discovered in 1499 by the Spanish explorer Alonso de Ojeda, the lake lies in the extremely hot, humid lowlands of the Maracaibo basin, a region that, almost enclosed by mountains, is semiarid in the north but has an average annual rainfall of 50 in. (127 cm) in the south. The basin is one of the major oil-producing areas of the world, and was developed beginning in 1918. Although petroleum production is the most significant economic activity locally, sugarcane, cacao, and livestock are raised. In addition, fish are caught in the lake, despite pollution from agricultural runoff and oil spills. Lake Maracaibo, with the Catatumbo River, its chief tributary, is a major artery of communication for products of the adjacent region and those of the Colombian-Venezuelan highlands. A dredged channel gives oceangoing vessels access to the lake. Cabimas and the port of Maracaibo are the principal cities on the lake. Gen. Rafael Urdaneta Bridge (c.5 mi/8 km long; completed 1962), spanning the lake's outlet, is one of the longest bridges in the world.