The site of the citadel is a platform nearly square and 2700 feet in circuit, standing about 200 feet above the level of the surrounding parts of the hill. Its walls were completely demolished By the Romans in 1191 and not a vestige of them is left. Sir William Gell thought, however, that he could discover the traces of four ancient gates, one on the west, another on the side of the Alban valley, a third on the eastern side, and not far from this last, a postern communicating with a steep and rocky path which descended to the Alban valley. Most of the ruins now visible belong to the mediæval fortress of the Dukes of Tusculum, and a few only of the quadrilateral blocks of the ancient enclosure are visible. In the Æquian and Volscian wars this citadel played an important part. It must therefore have been a fortress of considerable strength from very early times. Dionysius describes it as a very strong position, requiring but a small garrison to hold it, and adds that the whole country as far as the gates of Rome, is plainly visible from it, so that the defenders could see the Roman forces issuing from the Porta Latina. The city itself lay on the ridge of the hill westwards from the citadel. The area which it occupied is an oblong strip of ground about 3000 feet long, and from 500 to 1000 feet in width. On the north and south sides the limits of the city are clearly marked by the edges of the hill, but on the west they are not so easily defined. At the foot of the descent from the citadel are the ruins of a large water tank of an oblong shape divided into four compartments by three rows of piers, and immediately under this tank is a small theatre built of peperino, which was excavated by the dowager Queen of Sardinia Maria Christina in 1839 and 1840. This, with the exception of the theatres at Pompeii, is the most perfectly preserved in Italy. The walls of the scena are unfortunately destroyed, but the ground plan of it can still be traced. The stage, which abuts closely on the western side of the semicircular cavea, is 110 feet in length, and 20 feet in depth. It has the three usual entrances from the back, and one at each end. These open into a corridor and communicate with two chambers, probably used as dressing rooms by the actors. Nearly the whole of the fifteen rows of seats in the lower division are still preserved unbroken, but the upper part which contained, to judge by the height of the outer walls still remaining, about nine rows of seats, is entirely destroyed. [Sidenote: Other ruins.] [Sidenote: Gate and walls.]