Such were the fortifications of Carcassonne, the chief frontier fortress on the side of Aragon, and there can be little doubt that against the means of attack then employed, they were practically impregnable. The ancient Church of St Nazaire at Carcassonne may be taken as an example of the ruder form which the Romanesque style assumed in a district not far removed from Provence. It occupies the highest point of the height on which stands the ancient fortified _cité_ of Carcassonne. [Illustration: FIG. 115. ST NAZAIRE, CARCASSONNE.] The church is placed near the walls of the city, and the west end is elevated and fortified so as to form part of the defences. The entrance to the nave is by a twelfth century doorway in the north aisle. The building consists of two portions, which form a striking contrast with one another (Fig. 115); the nave of the eleventh century, and the Romanesque choir of the fourteenth, the former of a massive and gloomy design, the latter of the lightest and most elegant Gothic. The older portion consists of a central nave and two side aisles, separated by enormous piers, which are alternately plain cylinders and squares with an engaged column on each face. The bases of the piers vary greatly in form--none of them being of Roman design, but all set upon a great square block. The caps of the cylindrical piers differ considerably, but consist of large mouldings, with corbels and billet ornaments. The pier arches are circular, and the aisles lofty, and vaulted with round arches. Rising from the caps of the cylindrical piers are short columns, the caps of which carry the pointed transverse ribs of the tunnel vault of the nave, which is also pointed, and probably belongs to the twelfth century. The caps of these short columns, and of the attached shafts of the square piers, are all very large and bold, and seem to be founded on Roman designs. The light Gothic work of the choir, with its tall slender shafts, and walls composed almost entirely of mullions and stained glass, forms a brilliant termination to the vista of the ponderous nave. It belongs to a much later period than the latter, having been erected by Bishop Pierre de Rochefort, 1320-30. It is a palpable instance of the extension of the Gothic style of the Royal Domain along with that of the Royal Power, having been erected shortly after Carcassonne was united to France. Viollet-le-Duc considers this choir one of the most instructive instances of the scientific method of construction adopted by the Gothic architects of the fourteenth century; and he points out that the architect has endeavoured to keep up the idea of the ancient nave in the new work by preserving in the choir the plan of the nave piers--those of the central compartments being square, with attached shafts, while the others are round on plan. We shall now return to Aigues Mortes, which, it will be remembered, was reserved for consideration along with Carcassonne.