The development of this remarkable people had reached a considerable stage long before the beginning of the Roman rule over Egypt.[257] Its native seat, the Arabia Felix of the ancients, the region of Mocha and Aden, is surrounded by a narrow plain along the shore intensely hot and desolate, but the healthy and temperate interior of Yemen and Hadramaut produces on the mountain-slopes and in the valleys a luxuriant vegetation, and the numerous mountain-waters permit in many respects with careful management a garden-like cultivation. We have even at the present day an expressive testimony to the rich and peculiar civilisation of this region in the remains of city-walls and towers, of useful buildings, particularly aqueducts, and temples covered with inscriptions, which completely confirm the description of ancient authors as to the magnificence and luxury of this region; the Arabian geographers have written books concerning the strongholds and castles of the numerous petty princes of Yemen. Famous are the ruins of the mighty embankment which once in the valley of Mariaba dammed up the river Dana and rendered it possible to water the fields upwards,[258] and from the bursting of which, and the migration alleged to have been thereby occasioned of the inhabitants of Yemen to the north, the Arabs for long counted their years. But above all this district was one of the original seats of wholesale traffic by land and by sea, not merely because its productions, frankincense, precious stones, gum, cassia, aloes, senna, myrrh, and numerous other drugs called for export, but also because this Semitic stock was, just like that of the Phoenicians, formed by its whole character for commerce; Strabo says, just like the more recent travellers, that the Arabs are all traders and merchants. The coining of silver is here old and peculiar; the coins were at first modelled after Athenian dies, and later after Roman coins of Augustus, but on an independent, probably Babylonian basis.[259] From the land of these Arabians the original frankincense-routes led across the desert to the marts on the Arabian gulf, Aelana and the already-mentioned Leuce Come, and the emporia of Syria, Petra and Gaza;[260] these routes of the land-traffic, which along with those of the Euphrates and the Nile, furnish the means of intercourse between East and West from the earliest times, may be conjectured to be the proper basis of the prosperity of Yemen. But the sea-traffic likewise soon became associated with them; the great mart for this was Adane, the modern Aden. From this the goods went by water, certainly in the main in Arabian ships, either to those same marts on the Arabian gulf and so to the Syrian ports, or to Berenice and Myos Hormos, and from thence to Coptos and Alexandria. We have already stated that the same Arabs likewise at a very early time possessed themselves of the opposite coast, and transplanted their language, their writing and their civilisation to Habesh.