Destroyed the Kassites in Akkad and Sumer. Not long after, the new Assyrian capital, Nineveh, was built. It was very nice with a library and a zoo. The water supply was poor. The Assyrians were greatly hated. The Medes took control of Assyria in 612 BC and invaded Anatolia. The Chaldeans (New Babylonians) became the new masters of Mesopotamia. Their greatest cultural successes were in the field of astronomy. They studied the sky because they believed the gods lived there. The Persian Empire was ruled by Darius the Great from 522 to 485 BC. He spent years improving the administrative organization, then worked on expanding the empire. This empire lasted longer than all the others because people could keep their own laws as long as they paid taxes. The Persian army also allowed for greater protection from invasion. They used cuneiform writing borrowed from the Summerians. More unifying forces they used were the universal system of weights and measures, the highway system, the postal service and Zoroastrianism based on individual criteria.