Throughout the circumference of the _enceinte_ the curtain was strengthened by rectangular flanking towers having a front of forty-five, and a salience of rather more than thirteen feet.[85] These were separated from each other by intervals of ninety feet, or double the front of a tower. Only the lower parts of the towers are now in existence, and we have to turn to the representations of fortresses in the reliefs before we can restore their super-structures with any certainty. In these sculptures what we may call the head of the tower equals on an average from a fourth to a fifth of the height of the curtain. By adopting an elevation half way between these two proportions, M. Place has given to his towers a total height of 105 feet to the top of their crenellations, a height which is near enough to the 100 Grecian feet attributed by Diodorus to the Nineveh walls. The description borrowed by that writer from Ctesias, is, as we have shown, in most respects quite imaginary, but it may have contained this one exact statement, especially as a height of about 100 feet seems to have been usually chosen for cities of this importance. The parapets of the towers were corbelled out from their walls and pierced with loopholes, as we know from the reliefs. Each doorway was flanked by a pair of towers, the wall between them being only wide enough for the entrance. Our Plate V. will give a very exact idea of the general appearance of the whole _enceinte_. Including those of the palace mound, it has been calculated that the city of Sargon had one hundred and sixty-seven towers. Was there a ditch about the wall like that at Babylon? We are tempted to say yes to this, especially when we remember the statement of Herodotus that the earth taken from the ditch served to afford materials for the wall. Moreover such a ditch could have been easily kept full of water by means of the two mountain streams that flow past the mound. But the explorers tell us they could find no trace of such a ditch.[86] If it ever existed it has now been so completely filled up that no vestige remains. Upon each of its south-eastern, south-western and north-eastern faces the city wall was pierced with two gates. One of these, decorated with sculptures and glazed bricks, is called by Place the _porte ornée_, or state entrance, the other, upon which no such ornament appears, he calls the _porte simple_. On the north-western face there is only a _porte simple_, the palace mound taking the place of the state gateway. The plinth and the lower courses of burnt brick are continued up to the arches of these gates; the latter are also raised upon a kind of mound which lifts them about eight and a half feet above the level of the plain. In size and general arrangement these gateways were repetitions of each other. Our Figs. 50 in the first volume, 24 and 25 in this, show severally the present condition, the plan and the restored elevation of a _porte simple_.