Anciently it seems to have immediately overhung the Tigris, which has now moved off to the west, leaving a plain nearly a mile in width between its eastern edge and the old rampart of the city.

This rampart followed, apparently, the natural course of the river-bank; and hence, while on the whole it is tolerably straight, in the most southern of the three portions it exhibits a gentle curve, where the river evidently made a sweep, altering its course from south-east nearly to south.
The western wall at its northern extremity approaches the present course of the Tigris, and is here joined, exactly at right angles, by the northern, or rather the north-western, rampart, which runs in a perfectly straight line to the north-eastern angle of the city, and is said to measure exactly 7000 feet.

This wall is again divided, like the western, but with even more preciseness, into three equal portions.
Commencing at the north-eastern angle, one-third of it is carried along comparatively high ground, after which for the remaining two-thirds of its course it falls by a gentle decline towards the Tigris.

Exactly midway in this slope the rampart is broken by a road, adjoining which is a remarkable mound, covering one of the chief gates of the city.
At its other extremity the western wall forms a very obtuse angle with the southern, which impends over a deep ravine formed by it winter torrent, and runs in a straight line for about 1000 yards, when it meets the eastern wall, with which it forms a slightly acute angle.
It remains to describe the eastern wall, which is the longest and the least regular of the four.

Tins barrier skirts the edge of a ridge of conglomerate rock, which here rises somewhat above the level of the plain, and presents a slightly convex sweep to the north east.