 This epic begins with the city. And the city is exemplified by the wall. Look at that wall, that most wondrous thing. So in order to have a city in Mesopotamia, you are going to have to have walls, protectable walls. There is no such thing here as a city without a wall. You need the wall to protect the food supply. Because when famine hits outside the city, you will get marauding tribes, uncivilized, coming in, rushing in to take your grain. So the walls are absolutely necessary.