The Land of Mesopotamia Mesopotamia is roughly 600 miles long (northwest to southeast) and 300 miles wide at its greatest extent in the north and some 100–150 miles wide in the south. To give some idea of distances, Ur is about 150 miles north of the head of the Persian Gulf and 220 miles south of modern Baghdad. Northern Mesopotamia was known generally in ancient times as Assyria and southern Mesopotamia as Babylonia. Babylonia was subdivided into Sumer (in the south next to the Persian Gulf)