The ancient structures closely associated with the Sumerian civilization include ziggurats, which were massive tiered temple complexes that served as religious and administrative centers. The most famous ziggurat is the Great Ziggurat of Ur, dedicated to the moon god Nanna. In addition to ziggurats, the Sumerians are known for their advancements in architecture, such as the use of arches and domes, as well as city walls and irrigation systems. These constructions not only reflect the Sumerians' architectural capabilities but also underscore their complex societal organization and religious beliefs, making them significant in ancient Mesopotamian history.