It will thus be seen that excavations conducted on the sites of the more famous cities of Sumer have not, with the single exception of Nippur, yielded much information concerning the earlier periods of history, while the position of one of them, the city of Isin, is still unknown. Our knowledge of similar sites in Akkad is still more scanty. Up to the present time systematic excavations have been carried out at only two sites in the north, Babylon and Sippar, and these have thrown little light upon the more remote periods of their occupation. The existing ruins of Babylon date from the period of Nebuchadnezzar II., and so thorough was Sennacherib's destruction of the city in 689 B.C., that, after several years of work, Dr. Koldewey concluded that all traces of earlier buildings had been destroyed on that occasion. More recently some remains of earlier strata have been recognized, and contract-tablets have been found which date from the period of the First Dynasty. Moreover, a number of earlier pot-burials have been unearthed, but a careful examination of the greater part of the ruins has added little to our knowledge of this most famous city before the Neo-Babylonian era. The same negative results were obtained, so far as early remains are concerned, from the less exhaustive work on the site of Borsippa. Abû Habba is a far more promising site, and has been the scene of excavations begun by Mr. Rassam in 1881 and 1882, and renewed by Père Scheil for some months in 1894, while excavations were undertaken in the neighbouring mounds of Deir by Dr. Wallis Budge in 1891. These two sites have yielded thousands of tablets of the period of the earliest kings of Babylon, and the site of the famous temple of the Sun-god at Sippar, which Narâm-Sin rebuilt, has been identified, but little is yet accurately known concerning the early city and its suburbs. The great extent of the mounds, and the fact that for nearly thirty years they have been the happy hunting-ground of Arab diggers, would add to the difficulty of any final and exhaustive examination. It is probably in the neighbourhood of Sippar that the site of the city of Agade, or Akkad, will eventually be identified.