It is plain from the description which has just been given that the characteristic features of the site attain their greatest development in that part of the enclosure which is most remote from the shore; that it is there the protecting gulfs are deepest, and the rock loftiest which they flank. Indeed, during the Byzantine and earlier Comnenian periods the fortress was confined to this upper portion, and the outer wall on the side of the sea was drawn from gulf to gulf at a distance of about 460 yards from the present margin of the shore. A few sentences may suffice to present the plan of the fortifications, as it may be traced among the ruins that remain. At the very head of the formation came the keep and citadel, the outer wall being drawn across the narrow isthmus between the two ravines; this was the weakest point in the whole circumference of the fortress, and the works were strongest upon this side. Built into this outer wall stands a massive square tower, which rises boldly above the battlements and faces the approaches from the south. The ground shelves upwards almost from the immediate foot of the tower to the amphitheatre of hills which surround the bay. Thus the fortress is commanded by the slopes upon the south, where already it is by nature most vulnerable. It was from the south that its assailants delivered their principal attacks: the Goths, the Georgians, the Seljuks, the Turkomans, the Ottoman Turks. All the space inside the wall and between the two ravines was filled up at this uppermost part of the fortress, first by the keep, and then by the palace itself; the citadel served as the kingly residence, and the wall with the bold windows which rises along the edge of the western ravine was alike fortress and palace wall. This uppermost fortress or citadel, with the palace of the king, was separated from the lower but more extensive portion of the site by a cross-wall, equal in height to the walls along the ravines, and supported at either end by towers. So much loftier is this upper stage than the stage which lies below it that, whereas the palace, which occupies the most elevated point, towers high above the battlements of the cross-wall, the base of this wall itself overtops the highest buildings of the second and lower stage.