Why were ziggurats the tallest buildings in the Sumerian cities?

Ziggurats were the tallest buildings in Sumerian cities primarily due to their religious significance, serving as temples dedicated to the gods. Their elevated structure symbolized a connection between the heavens and the earth, allowing priests to perform rituals closer to the divine. Additionally, the use of mud-brick construction and a tiered design enabled these monumental structures to rise above the surrounding landscape, making them prominent landmarks within the city.