Seleucia, the name of numerous ancient cities of Asia, situated in Assyria, Margiana, Syria, Mesopotamia, Cilicia, Pamphylia, Pisi-dia, Caria, and other countries. I. Seleucia on the Tigris was founded by Seleucus I. of Syria, on the right bank of that river, near its junction with the royal canal of Babylonia, and opposite the mouth of the Delas (now Diala) river, a little S. of the modern city of Bagdad. Commanding the plains of the Tigris and Euphrates, and the principal caravan roads of Assyria and Babylonia, and peopled by settlers from various countries of western Asia, it rapidly rose in wealth and splendor, eclipsing Babylon, until it was in its turn eclipsed by Ctesiphon, built by the Parthians on the opposite bank. The later wars of the Romans against that people proved destructive to Seleucia. It had more than half a million inhabitants in the 1st century, in the 2d was burned by Trajan and Lucius Aurelius Verus, and captured by Septimius Severus, and in the expedition" of Julian against the Persians in the 4th century was found deserted.
Seleucia Pieria, a strong fortress of northern Syria, also founded by Seleucus I., was built at the foot of Mt. Pieria, on a rock overhanging the Mediterranean, a few miles N. of the mouth of the Orontes, and W. of Antioch, with which it was simultaneously founded, and of which it formed the seaport. It surrendered to Ptolemy III. of Egypt, was recovered by Antiochus the Great, and in the later period of the Syrian kingdom became independent. Under the Romans it rapidly decayed. Considerable ruins of its harbor, fortifications, and necropolis are still to be seen.