 This pier design, known as "pilier cantonné", was strong, simple, and elegant, and permitted the large stained glass windows of the clerestory, or upper level.most notably Gothic churches.Although the sculpture on the portals at Chartres is generally of a high standard, the various carved elements inside, such as the capitals and string courses, are relatively poorly finished (when compared for example with those at Reims or Soissons) – the reason is simply that the portals were carved from the finest Parisian limestone, or ' 'calcaire' ', while the internal capitals were carved from the local ""Berchères stone"", that is hard to work and can be brittle.