In 539 BC Cyrus peacefully took possession of Babylon, and the kingdom of Iranian peoples, taken over by the Achaemenian dynasty from the Medes, expanded to become the first real world-empire of ancient history. Under the Seleucids and the Parthians the site of the Mesopotamian capital moved a little to the north on the Tigris to Seleucia and Ctesiphon. When Alexander the Great at last halted his victorious march, the eastern frontier of the Achaemenian kingdom, he saw as the final goal of his desires the rebuilding of Babylon. Parthian art or Mesopotamian art of the Arsacid period worked with borrowed elements of Greek fashion, but these quickly lost their essential character. The drama of the foundation of a new world-religion, which shook both the Christian west and Zoroastrian Iran, was also enacted in Mesopotamia. It was the assimilation of ancient oriental culture into the Achaemenian empire and its Iranian successor states that first gave "Babylonism" the vast world-historical pers.