The Nile flows through Cairo and forms Egypt’s fertile delta. At about 6,650 kilometres, it is traditionally described as the world’s longest river, although measurements comparing it with the Amazon depend on how sources and mouths are defined.
The river has two major tributaries: the White Nile, whose headwaters extend toward the Great Lakes region, and the Blue Nile, which rises in Ethiopia. They meet at Khartoum in Sudan before the combined river continues north through Egypt to the Mediterranean Sea.
For thousands of years, Nile floodwaters deposited fertile silt across the valley and delta, supporting dense settlement in an otherwise arid landscape. The Aswan High Dam, completed in the 1970s, greatly reduced seasonal flooding and created Lake Nasser, but it also limited the natural delivery of silt to downstream farmland.