The Nile is the longest river in the world, stretching north for approximately 4,000 miles from East Africa to the Mediterranean. Studies have shown that the River (Iteru, meaning, simply, River, as the Egyptians called it) gradually changed its location and size over millions of years. The Nile flows from the mountains in the south to the Mediterranean in the north. Egyptians traveling to other lands would comment on the "wrong" flow of other rivers. For example, a text of Tuthmosis I in Nubia describes the great Euphrates river as the "inverted water that goes downstream in going upstream."
Three rivers flowed into the Nile from the south and thus served as its sources: the Blue Nile, the White Nile and the Arbara. Within the southern section between Aswan and Khartoum, land which was called Nubia, the River passes through formations of hard igneous rock, resulting in a series of rapids, or cataracts, which form a natural boundary to the south. Between the first and second cataracts lay Lower Nubia, and between the second and sixth cataracts lay upper Nubia.
Along most of its length through Egypt, the Nile has scoured a deep, wide gorge in the desert plateau. At Aswan North of the first cataract the Nile is deeper and its surface smoother. Downstream from Aswan the Nile flows northerly to Armant before taking a sharp bend, called the Qena. From Armant to Hu, the River extends about 180 kilometers and divides the narrow southern valley from the wider northern valley.
Southern Egypt, thus being upstream, is called Upper Egypt, and northern Egypt, being downstream and the Delta, is called Lower Egypt. In addition to the Valley and the Delta, the Nile also divided Egypt into the Eastern and Western Deserts.