North of the Khosr, between the city wall and that river, which there runs parallel to the wall and forms a sort of second or outermost moat, there are traces of a detached fort of considerable size, which must have strengthened the defences in that quarter.

South and south-east of the Khosr, the works are still more elaborate.

In the first place, from a point where the Khosr leaves the hills and debouches upon comparatively low ground, a deep ditch, 200 feet broad, was carried through compact silicious conglomerate for upwards of two miles, till it joined the ravine which formed the natural protection of the city upon the south.

On either side of this ditch, which could be readily supplied with water from the Khosr at its northern extremity, was built a broad and lofty wall; the eastern one, which forms the outermost of the defences, rises even now a hundred feet above the bottom of the ditch on which it adjoins.

Further, between this outer barrier and the city moat wall interposed a species of demilune, guarded by a double wall and a broad ditch and connected (as is thought) by a covered way with Neneveh itself.