Ziggurats were built in the city-sumer as

According to Herodotus, at the top of each ziggurat was a shrine, although none of these shrines have survived. One practical function of the ziggurats was a high place on which the priests could escape rising water that annually inundated lowlands and occasionally flooded for hundreds of miles, for example the 1967 flood. Another practical function of the ziggurat was for security. Since the shrine was reachable only by way of three stairways, a small number of guards could prevent non-priests from spying on the rituals at the shrine on top of the ziggurat, such as initiation rituals such as the Eleusinian mysteries, cooking of sacrificial food and burning of carcasses of sacrificial animals. Each ziggurat was part of a temple complex that included a courtyard, storage rooms, bathrooms, and living quarters, around which a city was built