The Mesopotamian cultures (Sumerians, Babylonians, Assyrians, and Chaldeans) were very knowledgeable about the motions of the Sun, Moon, planets, and stars. They mapped the twelve constellations of the zodiac. Their towering temples, called ziggurats, may have been used as astronomical observatories. Arab astronomers built great observatories throughout the Islamic empires of a thousand years ago, and we still use Arabic names for many of the best-known stars in the sky.