The municipal organisation was moulded in the main after the pattern of the Greek municipality of the Roman empire; the designations for magistrates and council[88] and even those of the colony are in the Palmyrene texts retained for the most part from the imperial languages. But in administration the district retained a greater independence than is elsewhere assigned to urban communities. Alongside of the civic officials we find, at least in the third century, the city of Palmyra with its territory under a separate “headman” of senatorial rank and Roman appointment, but chosen from the family of most repute in the place; Septimius Hairanes, son of Odaenathus, is substantially a prince of the Palmyrenes,[89] who was doubtless not otherwise dependent on the legate of Syria than were the client-princes on the neighbouring imperial governors generally. A few years later we meet with his son,[90] Septimius Odaenathus, in the like position--indeed even raised in rank--of hereditary prince.[91] Similarly, Palmyra formed a customs-district apart, in which the customs were leased on account, not of the state, but of the community.[92] [Sidenote: Commercial position of Palmyra.] The importance of Palmyra depended on the caravan-traffic. The heads of the caravans (συνοδιάρχαι), which went from Palmyra to the great entrepôts on the Euphrates, to Vologasias, the already mentioned Parthian foundation not far from the site of the ancient Babylon, and to Forath or Charax Spasinu, twin towns at its mouth, close on the Persian Gulf, appear in the inscriptions as the most respected city-burgesses,[93] and fill not merely the magistracies of their home, but in part also imperial offices; the great traders (ἀρχέμποροι) and the guild of workers in gold and silver testify to the importance of the city for trade and manufactures, and not less is its prosperity attested by the still standing temples of the city and the long colonnades of the city halls, as well as the massy and richly decorated tombs. The climate is little favourable to agriculture--the place lies near to the northern limit of the date palm, and does not derive its Greek name from it--but there are found in the environs the remains of great subterranean aqueducts and huge water-reservoirs artificially constructed of square blocks, with the help of which the ground, now destitute of all vegetation, must once upon a time have artificially developed a rich culture. This riches, this national idiosyncrasy not quite set aside even under Roman rule, and this administrative independence, explain in some measure the part of Palmyra about the middle of the third century in the great crisis, to the presentation of which we now return. [Sidenote: Capture of the emperor Valerian.]