Mommsen and others have pointed out the favourable position of Rome as an emporium. From the very first that city became the commercial centre of the neighbouring populations. Built in the centre of a circus of hills, and on the banks of a navigable river, not far from the sea, it likewise possessed the advantage of lying on the frontiers of three nations—Latins, Sabines, and Etruscans. When Rome had conquered the neighbouring territories it undoubtedly rose into importance as a place of commerce. This local traffic, however, would never have converted Rome into a great city. Its position is not to be compared with that of places like Alexandria, Constantinople, or Bombay, upon which the world’s commerce converges as a matter of course. On the contrary, its situation hardly favours commerce. The Apennines, which environ the territory of Rome in a huge semicircle, constituted a formidable obstacle until quite recently, and were avoided by merchants; the sea near Rome is treacherous, and even the small galleys of the ancients could not enter the inefficient harbour at Ostia without risk. The power of Rome, therefore, depended but in a small measure upon commercial advantages resulting from geographical position. It is its central position to which that city is mainly indebted for its greatness, and which enabled it to weld the whole of the ancient world into a political whole. Three concentric circles drawn around the city correspond with as many phases in its development. During their first struggles for existence the Romans enjoyed the advantage of occupying a basin of limited extent, shielded on all sides by mountains. When Rome had exterminated the inhabitants of these mountains the remainder of Italy naturally gravitated towards her. The plains of Cis-and Transpadana in the north presented no obstacles, whilst the resistance of the uncivilised tribes of the mountain regions of the south was soon broken, for they found no support amongst the Greek colonies scattered along an extensive coast. Nor were the populations of Sicily, Sardinia, and Corsica sufficiently united to offer an effective resistance to the organized forces of the Romans, who were thus able to extend their power over all the countries comprehended within the second concentric circle referred to. {186} It happened that the plains of Northern Italy and Sicily were both rich granaries, which enabled the Romans to push forward their conquests. The whole world of the Mediterranean gravitated towards Rome and Italy: Illyria, Greece, and Egypt in the east, Libya and Mauritania in the south, Iberia in the west, Gaul in the north-west, and the transalpine countries in the north. [Illustration: Fig. 50.—ROME AND THE ROMAN EMPIRE.]