The long dynasty of the Elamite national kings, who ruled over Elam for nearly 1, 500 years, was, after a long and unequal struggle, brought to a close by the Assyrians under Assurbanipal in about 640 B.C. The Assyrian rule in Elam collapsed soon after the death of this conqueror in 625 B.C. The Elamite kingdom was thereupon divided into two different monarchies, Perso-Anzanite and Susiano-Babylonian. After the defeat of the last Babylonian king Nabunaid in 539 B.C., Cyrus the Great, the fourth Perso-Anzanite king, became the founder of the great Achæmenian dynasty. After the death of his son and successor Cambyses and the suppression of the revolt of Gaumata the Magian, Darius the Great, a descendant of the younger branch of the Achæmenides, became the inheritor of the vast empire of Cyrus in 521 B.C. During the early years of his reign he had to subdue many revolts in different provinces of his empire. It seems that the political troubles ended in about 518 B.C., and the great king began the work of rebuilding and embellishing Susa, which he had made the capital of his empire, as well as Persepolis and Hamadan. This work was carried on with great zeal by his son Xerxes, who was a far greater builder than his father. Owing to the free use of huge blocks of stone in the palatial buildings of Persepolis their ruins have for centuries drawn the attention of travellers by their colossal dimensions and gigantic magnificence. But the memories of the palaces of Susa and Hamadan are preserved only in certain allusions in the Bible and in the works of ancient writers. Their traces were nearly wiped out by time, whose ravages the less durable materials, bricks and wood, of which they were constructed, could hardly resist.