The Semna gorge, at the southern edge of ancient Egypt, was the narrowest part of the Nile valley. It was here, at this strategic location, that the 12th Dynasty pharaohs built a cluster of four mud-brick fortresses: Semna, Kumma, Semna South and Uronarti — all covered by the waters of Lake Nasser since the completion of the Aswan Dam in 1971.