built the chapel of St. Margaret. Its keystones illustrate the sculpture of the period.
The largest of the chapels, being at the same time the most beautiful and interesting one, is St. Mary's, also called the Royal Chapel, on a square ground plan, and crowned with a fine rib vault. The outline of the choir is a rectangle, composed of four smaller ones which correspond to the four compartments of the vault. Ten windows light the interior of the choir. By the heightening of the ambulatory walls in the eighteenth century the choir itself was darkened. Below the windows are the archways which formerly served both for communication between the choir and the ambulatory, and for the admission of light into the latter.
The cathedral was at first dedicated to St. Salvator, later to St. Wenceslaus. This is also illustrated by the keystones of the vaulting, which give historical evidence of the tendencies of worship: they show relief images of St. Wenceslaus, St. Stanislas, and St. Margaret. The choir is built of mixed material, partly brick, partly sandstone ashlars. The middle aisle, of later date, but said to have been ready before 1349, is constructed, on its inside, of limestone and freestone ashlars. The brickwork of the choir is set in "Polish" fashion, that is to say, with constant alternation of black borders and red stretchers. Both the middle aisle and the side aisles were included in the plan of the Romanesque basilica; some obliquity of the middle aisle's axis was occasioned by the fact that the architect—whose name is unknown—could not precisely determine the fundamental direction, because the old church and fortress buildings were still standing. To the side aisles are aggregated the fine chapels which were also distributed somewhat irregularly, in place of different parts of the Romanesque church; thus the southern tower (visible in illustration 19) was refashioned, and the ground floor of it was transformed into a chapel which was dedicated first to St. Stephen, then to St. John of Kenty. The clock tower on the north side is older than the dome itself, although its outward side, especially
