At the time of the great Pharaohs, Cairo did not exist. The ancient capital of Memphis was too close to the south, and there was no reason for the Egyptians to establish another city here. However, things changed when a group of prisoners from the Mesopotamian city of Babylon rose in revolt. They needed a safe place to defend themselves, so they chose an elevation on the east bank of the Nile and called it Babylon after their birthplace (another theory claims that the name is a corruption of the old Egyptian word “Per-hapi-en-on” which means Estate of the Nile God at On). The selection proved advantageous, and subsequent rulers of Egypt (the Persians and the Romans) decided to garrison their troops here. The fort stood at the point where the river Nile changed from the single stream that flowed through Upper Egypt into the countless channels and canals that form the magnificent Delta and lead to the sea.