hollow gravity dam on the Alto (Upper) Paraná River at the Brazil-Paraguay border, north of the town of Ciudad del Este, Paraguay. In terms of power output, it is one of the world's largest hydroelectric projects. Its 18 massive turbine generators, located in the powerhouse at the base of the dam, are capable of generating 12,600 megawatts of electricity. Built as a joint venture by Paraguay and Brazil, the complex of dams and spillways curves across almost 5 miles (8 km) of the Alto Paraná River. The dam itself, built between 1975 and 1982, is 643 feet (196 m) high and consists of large concrete segments joined to form a hollow chamber. The upstream face is supported by two buttresses, and the downstream face is a simple concrete slab. It is the highest and largest hollow gravity dam in the world. Its reservoir stretches northward for about 100 miles (160 km), and it has totally submerged the formerly spectacular Guaíra Falls.