The entrance to the crypts is by stairs from the transepts or crossing. The staircases to the upper portion of the building are variously placed. At Notre-Dame-du-Port they are in the middle of the north end of the aisles; at Brioude, in the transepts, and also at the west end; and in this church, an enormous wooden stair leads from the south door up to the chapel of S. Michael over the narthex. On the exterior the designs are as much alike as in the interior. The aisle walls are divided into bays by pilasters, above which arches are turned over the aisle windows, and then above are the windows lighting the triforia, which are generally more richly decorated than those below, and form part of an arcade with carved capitals and moulded bases. The walls are finished by a boldly-projecting cornice supported on large corbels. The transepts are buttressed at the angles, have a heavy engaged column in the centre, from which two arches spring, within which are pierced two windows; above these are other windows, either two or three lights, and the gable is either filled in with mosaic or pierced with more windows. It is on the exterior of the apse that the main effort at display is made, and the more ornate examples of the style, as Notre-Dame-du-Port, Issoire, and Brioude, are singularly rich in their effort. The two former examples are of very nearly the same date (about A.D. 1080 to A.D. 1130); the latter is considerably later (probably _circa_ A.D. 1200). I will describe Notre-Dame-du-Port first. Here the transept-chapels are much lower than those of the chancel, and the latter (four in number) have cornices below the cornice of the aisle, and gable walls are raised on the aisle walls to receive their roofs, which would otherwise run back to the clerestory. There are windows between each of the chapels, and a great part of the beauty of the effect, both internally and externally, is to be attributed to this fact. I am not sure that the whole arrangement is not a modification of the original plan, for on close examination I found that the labels of the large windows between the chapels are returned and mitre with another label against which the chapels are built, and which might very well have formed part of an arcade pierced at intervals with windows. In the neighbourhood, about half-way between Clermont and Issoire, at S. Saturnin, there is a church precisely similar to what this would have been without its chapels, and the eccentric position of the chapels at Notre-Dame-du-Port, there being none opposite the centre,[55] would be just such as would have been rendered necessary if it had been desired to add them after the work had progressed somewhat towards completion. In any case, however, there could not have been any great interval of time between them, and probably the chapels and the clerestory are of exactly the same age. The whole of this apse is full of beautifully inlaid patterns, made with red and black scoriae and white stone.