Towns and their Defences. 63 that we know nothing, and it is quite possible that after the death of Sargon it may have been practically abandoned, but because, of all the cities of Assyria, it is that whose line of circumvallation has been best preserved and most carefully studied (Vol. I. Fig. 144). Like all inhabited places of any importance Dour-Saryoukin was carefully fortified. Over the whole of Mesopotamia the words town and fortress seem to have been almost convertible terms. The nature of the soil does not lend itself to any such distinctions as those of upper and lower city, as it does in Italy and Greece ; there was no acropolis, to which the inhabitants could fly when the outer defences were broken down. In case of great need the royal palace with its massive gates and cincture of commanding towers might be looked upon as a citadel ; while in Babylon and some other towns several concentric lines of fortification made an attack more arduous and prolonged the defence. But, neverthe- less, the chief care of the Mesopotamian engineers was given to the strengthening of the external wall, the enceinte, properly speaking. At Khorsabad this stood on a plinth three feet eight inches high, above which began the sun-dried brick. The whole is even now nowhere less than forty-five feet high, while in parts it reaches a height of sixty feet. If we remember how greatly walls built of the materials here used must have suffered from the weather, we shall no longer be astonished at the height ascribed by Herodotus to the walls of Babylon : "These were, he says, 200 royal cubits (348 feet) high.' 1 This height was measured, no doubt, from the summit of the tallest towers into the deepest part of the ditch, which he adds, " was wide and deep." It is possible that the interpreters who did the honours of Babylon to the Greek historian exaggerated the figures a little, just as those of Memphis added something to the height of the pyramids. That the exaggeration was not very great is suggested by what he says as to the thickness of the wall ; he puts it at fifty royal cubits, or eighty-six feet six inches. Now those of Khorsabad are only between six and seven feet thinner than this, and it is certain that the walls of Babylon, admired by all antiquity as the masterpieces of the Chaldaean engineers, must have surpassed those of the city improvised by Sargon both in height and thickness. 1 Herodotus, i. 178.