Within 30 km of its source at Lake Tana, the Blue Nile River enters a canyon which it does not leave for 400 km. From all over the highlands, huge rivers pour into the Blue Nile Gorge. For a million years the Blue Nile has been carving this huge gash through the Ethiopian Highlands. Nearly 20km wide and over 600km long, this is Africa's own Grand Canyon. The Grand Canyon in Arizona, U.S.A. and the Blue Nile Gorge have their similarities and differences.