In approaching the town from the north the PORTE DE NIMES (Fig. 119) is first seen in front, while a long vista of the northern wall with its towers stretches to the left, and the Tour de Constance terminates the view to the right. This gateway has as usual a large strengthening round tower on each side, containing guardrooms, &c., and is so arranged as to form an independent post. Till the fourteenth century, gateways of this description were defended with folding gates, portcullis, machicolations (or apertures in the vault over the entrance passages), and with _bretêches_ or hoardings projecting over the entrance, pierced with single, double, or even triple tiers of loopholes from which to attack the assailants. But there were as yet no drawbridges. At the Porte de Nimes evidences may be observed of a drawbridge, wrought with long balanced beams or levers passing through the wall, having been used; but it has evidently been introduced at a later time. The walls of Aigues Mortes were entirely surrounded with a wet ditch (a few indications of which still remain), but it has for the most part been filled up and converted into a promenade. The ditch would be crossed with moveable wooden bridges which could be easily removed or destroyed. A projecting stone balcony is corbelled out from one of the round towers of the Porte de Nimes. This was no doubt a station from which audience could be given to heralds or others wishing to communicate with the [Illustration: FIG. 119. PORTE DE NIMES, AIGUES MORTES.] town without the necessity of opening any of the gates or other defences. The fortifications present on plan a right angled parallelogram about 600 yards from east to west, by 150 yards from north to south, with a curved portion cut out of the north-west angle. At this point stands the donjon, or Tour de Constance (_see_ Fig. 116), built by St Louis, as above mentioned, on the site of the ancient Tour de Matafère in order to form the citadel of the town. This tower is of the simplest possible design, being a plain cylinder about 70 feet in diameter, with a talus or slope near the base. It is about 100 feet high, and was no doubt originally crowned with overhanging hoardings, and when fully equipped would present an appearance not unlike the well known great Keep of Couci Castle. The Tour de Constance was surrounded with a special ditch, and was connected with the town walls by means of narrow wooden gangways, which could be easily removed. The top has been altered in the sixteenth century, and made into a platform, and provided with a parapet suitable for guns. Above the circular staircase in the thickness of the wall the watch turret rises to a considerable height, and is crowned with the iron grille which for long contained the fire which illumined the canal, and served as a beacon to the ships.