The ancient Egyptians believed that at first there was nothing but water. Then a mound appeared from the water. This creation myth reflects their yearly Nile flood, when the river’s waters covered the land, and then life-giving silt emerged as the waters receded.
Each temple they built represented that primordial mound of creation. In temple architecture, that mound was represented by a gradual rise in ground level between the entrance and the innermost shrine. Every temple also had a sacred lake, like the one above at Karnak, and each temple was surrounded by an undulating mudbrick wall. Because of course something as minor as a wall need to have a meaning, it is thought that the undulating wall represents the primordial ocean that the mound of creation rose from.