I doubt very much whether any part of the existing Cathedral is of the age of the church whose erection is recorded by Don Pelayo, except perhaps the external walls of the apse. Its general character is thoroughly that of the end of the twelfth or early part of the thirteenth century, with considerable alterations and additions at later periods; and we may safely assume that the chevet, commenced in A.D. 1091, was continued westward very slowly and gradually during the following hundred years or more. The ground-plan will show the very singular disposition of the plan; in which the chevet, with its double aisle and semi-circular chapels in the thickness of the walls, is, I think, among the most striking works of the kind in Spain.[172] The external wall of the apse is a semi-circle divided into bays by buttresses of slight projection alternating with engaged shafts. The chapels do not therefore show at all in the external view; and indeed all that does appear here is a projecting tower of vast size pierced with a few very small windows--mere slits in the wall--and flanked on either side by the wall and towers of the town. It is finished at the top by a corbel-table and lofty battlemented parapet; and behind this again, leaving a passage five feet and a half in width, is a second and higher battlemented wall, from within which one looks down upon the aisle-roof of the chevet, and into the triforium and clerestory windows of the central apse. From below very little of the apse and flying buttresses which support it are seen; and one is more struck perhaps by the strange unlikeness to any other east-end one has ever seen, than by any real beauty in the work itself; though at the same time it is pleasant to see that not even so difficult a problem as that of a windowless fortified chevet presented any serious difficulty to these old architects. [Illustration: No. 21 AVILA CATHEDRAL p. 164. INTERIOR OF AISLE ROUND THE APSE.] [Illustration: East End, Avila Cathedral.]