To the west are two large square towers; to the south a cloister added in 1376; and at the end of the north transept a chapel built at the end of the fifteenth century and entered by a large archway well carved with rich early renaissance ornament. If there is no advance from the romanesque plan of older churches, there is none in construction. All the arches are pointed, but that is the only direction in which any change has been made. The piers are all cross-shaped with a large half-shaft on each of the four main faces and a smaller round shaft in each angle. The capitals have square moulded abaci, and are rather rudely carved with budlike curled leaves; the pointed arches of the arcade are well moulded, and above them runs a continuous triforium gallery like that in the nave at Lisbon, but with small pointed arches. The main vault is a pointed barrel with bold ribs; it is held up by a half-barrel over the aisles, which have groined vaults with very large transverse arches. The galleries over the aisles are lit by small pointed windows of two lights with a cusped circle between, but except in the lantern which has similar windows, in the transept ends and the west front, these are the only original openings which survive. (Fig. 20.) Both transepts have large rose windows, the northern filled with tracery, like that, common in Champagne, radiating towards and not from the centre. The southern is more interesting. The whole, well moulded, is enclosed in a curious square framing. In the centre a doubly cusped circle is surrounded by twelve radiating openings, whose trefoiled heads abut against twelve other broad trefoils, which are rather curiously run into the mouldings of the containing circle. Over the west porch is a curious eight-light window. There are four equal two-light openings below; on the two in the centre rests a large plain circle, and the space between it and the enclosing arch is very clumsily filled by a rib which, springing from the apex of either light, runs concentrically with the enclosing arch till it meets the larger circle. The whole building is surmounted by brick battlements, everything else being of granite, resting on a good trefoil corbel table, and, as the roofs are perfectly flat, there are no gables.