What is the difference between upper Nubia and lower Nubia?

Upper Nubia refers to the southern part of the region, extending from the First Cataract of the Nile at Aswan to the area around Khartoum in Sudan. It is characterized by its mountainous terrain and historical significance as a center of ancient cultures, including the Kingdom of Kush. Lower Nubia, on the other hand, is located to the north, stretching from the First Cataract to the Nile Delta, and is generally flatter with more fertile land. The two regions differ in geography, cultural history, and archaeological significance.