=22. Rise of great cities.=—Some indication of the development of commerce, and of the rearrangement of its important centers, can be got from a study of the great cities of the ancient world. Before the time of Alexander there were only three cities of the Mediterranean with a population of over 100,000, Syracuse, Athens, Carthage; none of these had a population far above that figure. About 200 B.C., scarcely more than a century afterward, there were four cities with a population over 200,000, Alexandria, Seleukia, Antioch, Carthage; one city with a population far above 100,000, Syracuse; and of cities with a population about 100,000 there were Corinth, Rome, Rhodes, Ephesos, and possibly others. The names of some of these cities are already familiar to us. Carthage was enjoying its last century of commercial greatness, before Rome robbed it of its influence in the northern Mediterranean. Syracuse was the chief Greek colony of the West, destined also to fall under the Roman power just before 200. Other names, however, are entirely new to history, or first became of great importance at this time, and the best idea of the commerce of the period can be got by considering the reasons for their greatness. =23. Alexandria, Seleukia, Antioch.=—Alexandria, as its name suggests, was founded by the Macedonian conqueror. It was situated on a tongue of land between a lagoon and the sea, near the most western of the mouths of the Nile. It had a double harbor, formed by the island Pharos, which has given the name for lighthouse in some of the modern languages (French, _phare_, Italian, _fáro_), as the most celebrated lighthouse of antiquity was erected there. Alexandria furnished the only good harbor for large vessels on the coast of Egypt; it had access to the Nile, tapping one of the great granaries of antiquity, and connected with the Red Sea through the canal that ran from the Nile to the Bitter Lakes. It was at the point where the sea-route from the far East reached the Mediterranean, and it became by right the greatest market and the largest city that the world had known. Next to it in size and importance came two other cities, Seleukia and Antioch, which were founded even later than Alexandria. Seleukia, on the Tigris, took the place of the earlier Babylon and the later Bagdad; it was situated in a rich plain at the points where the routes from the Persian Gulf and the Persian highlands met on their way westward. Antioch was at the focus of the routes by which the trade with inner Asia was carried on. Situated at a point where the Euphrates approaches to within a few days’ march of the coast, and where the valley of the Orontes offers the best means of reaching the sea from the interior, it had the full benefit of the revival of eastern commerce which followed the conquests of Alexander and the enlightened rule of his successors.