The three stages of the western towers are, I think, respectively of the twelfth, thirteenth, and fifteenth centuries. The second or intermediate stage is arcaded, and has its angles planned with a shaft set in a broad splay precisely in the mode we see so commonly adopted in the Segovian towers.[177] The upper stage is finished with gables on each face, the gable being fringed with a line of granite trefoils in not very good taste. Gil Gonzales Dávila[178] says that the tower of this church was built by alms in A.D. 1440. He refers, no doubt, to the upper stage, the design of which agrees with this statement. I was not able to learn how it had originally been roofed; but my impression is that it probably had two stone gabled roofs intersecting each other. In addition to the western door there is another fine entrance on the south side of rather earlier date than the other, and now always in use as the ordinary entrance to the church. Descending here by some steps from the cloister, we find ourselves in the impressive interior, and are at once struck by some features which are of rare occurrence in this part of Spain. The columns are of very bold, perhaps heavy, design, and rest on circular bases. Their front portion is carried up on a bold and massive groining pier in front of the main wall; the arcades are severely simple, the arches semi-circular, and the capitals richly carved. A carved stringcourse is carried round the church above the arches, and there is the very uncommon arrangement (in this country) of a well-developed triforium; each bay here having a round-arched opening, subdivided into two smaller openings, divided by a massive column with sculptured capital. Another stringcourse divides the triforium and clerestory, which has also round-arched windows of one light. The vaulting, both in the nave and aisles, is quadripartite, the only remarkable feature in it being the massive size of the ribs. The three eastern apses are vaulted with waggon-vaults over their western compartments, and semi-domes over the apses, and the transepts are roofed with waggon-vaults. All the latter have cross arches or ribs below them carried on engaged shafts, and the side walls of the chancel and chancel-aisles are arcaded below the vaulting.