The Aswan High Dam (top of photo) is 4 km (2.5 mi) across and 111 m (364 ft) high. Completed in 1971, it was constructed to supply cheap hydroelectric power to both Egypt and Sudan by impounding, controlling, and regulating the flood waters of the Nile River in Lake Nasser, the world's second largest artificial lake. The lake extends over 800 km (500 mi) in length, covers an area of some 5,200 sq km (2,000 sq mi) and is as much as 107 m (350 ft) deep at the face of the dam. Click on photo for higher resolution. Image courtesy of NASA.