Philostratus remarked that a daring besieger might run in towards the west, between the river and the city, and attempt an assault towards the salient of the west front, which commanded a rather gentle escarpment. From the square tower, B, to the river, and set back a little, so as to be flanked by the western face of this tower, he formed a _vallum_, with a square tower at its extreme end, commanding the water-course. Further back was constructed a wooden bridge, connecting the two banks, and passing over the island of sand, C. Along the two escarpments the engineer followed almost exactly the sinuosities of the edge of the plateau, but placing the gates in the re-entering angles. Two gates were disposed on the western front, and one on the eastern, very near the situation of the ancient entrance to the _Oppidum_ on that side. These three gates were each flanked by two towers, like those on the north. The inclosure of the city, formed of a rampart rising twenty feet above the level of the ground, including the battlement, and nine feet thick, was thus strengthened by thirty-six towers, without reckoning those of the gates. At the southern extremity, on the site of the ancient retreat of Catognatus, was erected a _castellum_, or stronghold, separated from the city by a battlemented wall, and about one hundred and eighty feet away from the ramparts. At the southern extremity of the rampart, a square tower had to be built of greater height than the others, to overlook the vale of Abonia. Beneath this tower an egress was contrived, abutting on a massive wall, following the declivity of the ground, and crenelated on both sides; from the summit of which a descent could be made into the work, E, commanding the junction of the rivulet with the river, and the stone bridge constructed there. Upon the other bank was built a vast _tête de pont_. The eastern gate was furnished with an outwork commanding the road, G; on the northern flank of the north-west entrance a guardhouse commanded the vicinity of the gate. The approaches were improved, and a wooden bridge was thrown across at H, with a _tête de pont_ and work commanding the confluence of roads at that point. Building was prohibited on the western declivities--once occupied by houses and gardens--within a distance of one hundred and ten paces from the ramparts, or the military road, I; that is, habitations were allowed to remain or to be built outside the military bounds.[6] Inside the city, through the confusedly-grouped clusters of ancient houses, Philostratus had new roads cut,[7] with a view to establish a communication between the gates, and to facilitate the defence. At F was placed a forum, with a temple to Apollo at I (for Julian had caused a little Christian church, previously built in the city, to be demolished). A basilica was built at M, a _curia_ at N; and at T baths were erected. In the lower town, quay-walls, Q, kept the river within