The civilization famous for its ziggurats and advances in astronomy is the Sumerian civilization, which thrived in ancient Mesopotamia (modern-day Iraq) around 4500-1900 BC. Sumerians are regarded as one of the first known civilizations, known for their impressive architectural structures called ziggurats—massive terraced buildings that served religious purposes. Their advances in astronomy included creating a calendar based on lunar cycles, understanding celestial bodies, and developing a sexagesimal number system, which is the basis for our 60-minute hour and 360-degree circle. Sumer's contributions laid the groundwork for subsequent civilizations' scientific and cultural developments.