The term 'Capital on the Nile' refers to two cities located along the Nile River in Africa. The first city is Khartoum, the capital of Sudan, which has 8 letters. It is located at the convergence of the Blue and White Niles and is the largest city in Sudan. The second city is CAIRO, the capital of Egypt, which has 5 letters. It is the largest city in Africa and is known for its ancient monuments, such as the Great Pyramids of Giza.