Sumerian and Babylonian peoples of ancient Mesopotamia created civilizations which had an artistic tradition of remarkable antiquity, variety, and richness, as revealed by excavations at Ur, Babylon, Uruk (Erech), Mari, Kish, and Lagash. With the ascent to power of Sargon of Akkad, Sumerian art reached new heights of expression, particularly in sculpture. The greatest known examples reflecting that splendor include a bronze head thought to be a portrait of Sargon himself. The Akkadians spread cuneiform writing throughout the Middle East. An Assyrian artistic style distinct from that of Babylonian Mesopotamian, and Sumerian art emerged c.1500 B.C. and lasted until the fall of Nineveh in 612 B.C. The characteristic Assyrian art form was the polychrome carved stone relief that decorated imperial monuments. The precisely delineated reliefs concern royal affairs, chiefly hunting and war making. Among the best known of Assyrian reliefs are the lion-hunt alabaster carvings showing Assurnasirpal II (9th cent. BC) and Assurbanipal (7th cent. BC). Babylonia was not to be reborn until Nebuchadnezzar divided the Assyrian lands with the Medes in 612 B.C. Under his rule the Babylonians developed to perfection one of their most striking arts: the great polychrome-glazed brick walls modeled in relief, the foremost example of which is the Ishtar gates of Babylon. Less than a century later Babylonia fell prey to more invasions, and the Persians, Macedonians, and Romans ruled it in succession. The great Mesopotamian civilizations were forgotten until archaeologists of the 19th century brought them to light again.