This is a 3D model of the Etemenanki ziggurat which was the tall step pyramidal tower in the city of Ancient Babylon. It was the tallest ziggurat in ancient Mesopotamia and is believed by quite a bit of historians to have been the inspiration for the biblical story of the tower of Babel. Most reconstruction have the structure shown with perfectly vertical walls but the walls were most likely at least slightly inward to provide structural stability since all other ziggurats were.