We shall have occasion to refer to the various systems of defence adopted in the different castles and towns to be visited, when attention will also be drawn to the differences of the systems adopted in the North and South. We shall also find a remarkable application of castellated features in the churches of the South, where, after the twelfth century, almost every ecclesiastical structure is carefully fortified. This produces in the churches of the South one of their most striking peculiarities, and gives them, instead of the light and gracefully aspiring character of the Northern Gothic structures, a reflection of the grim and stern aspect of the feudal castle. The peculiar church architecture just referred to, no doubt derived its origin from the constant state of alarm and disturbance in which the Southern provinces were kept by the Albigensian wars, and the attacks of the Moors and Corsairs by sea and land. Some place of refuge and defence was required by the harassed inhabitants, who naturally fled to the church and fortified themselves therein. Frequently the cathedrals were comprised within the precincts of the Bishop’s Palace, which was fortified like a feudal castle. The cathedral being the largest building was eagerly seized upon as an important part of the fortifications, and even when the design was in Northern Gothic, had externally at least to adopt many of the defensive features of the South. Of this remarkable illustrations occur at Narbonne, Béziers, and Fréjus. We have now rapidly sketched the various steps by which Roman architecture was gradually transformed, from being in its decorative features an imitation of the classic trabeated style, into an embodiment of the true principles of arcuated or genuine stone construction, as exhibited in the fully developed Gothic of the thirteenth century. We have seen that this was by no means a simple process, and that it was only accomplished by the ordeal of the destructive though purifying dissolution of the Dark Ages, whence the true spirit of Roman construction emerged, cleared to a great extent of the extraneous elements with which it had been so long encrusted. But although the true features of arcuated architecture now slowly began to be developed, they were both aided and retarded by the surviving relics of Roman art which existed in the West, as well as by the influence of the classic taste which continued to prevail, although in a modified and expanded condition, in the East. The country through which we are about to travel is remarkably favourable for the study of the effects of these various influences. We have already seen how rich it is in genuine Roman structures. In our further progress we shall note how these examples served as models for the revival of the architecture; for so closely were the ancient designs frequently followed that the new structures were almost complete resuscitations of the style of the Lower Empire.