Final answer:
Ziggurats were important in Sumerian civilization because they were major architectural accomplishments and served as places of worship and religious importance.
Step-by-step explanation:
Ziggurats were important in Sumerian civilization because they represented a major architectural accomplishment and were the centerpieces of the great cities. These massive structures were terraced step pyramids with a shrine or temple at the summit. Only authorized religious officials were allowed inside to tend to the cult statues and make offerings, making ziggurats places of worship and religious importance.