Beneath the Nile lies a canyon cut into the limestone bedrock, running from south of Aswan to the Giza Plateau. By the time it reaches Cairo, the canyon is 8,000 feet deep. That is deeper than a mile, and 1,500 feet deeper than the Grand Canyon.
Today it is filled with alluvium, so no one sees it. Clear that sediment out, and a sheer canyon 8,000 feet deep would sit right next to the Giza Plateau.