Why was travel more difficult in Nubia then in Egypt?

Travel in Nubia was more difficult than in Egypt primarily due to its rugged terrain, which included mountains and deserts, compared to the relatively flat and fertile land of the Nile Valley in Egypt. Additionally, the Nile River in Egypt provided a reliable and navigable route for transportation and trade, whereas Nubia had fewer navigable waterways. The lack of established infrastructure and the presence of hostile territories further complicated travel in Nubia. These factors combined made travel and communication more challenging in Nubia compared to its northern neighbor.