The paucity of stone in the province caused the creation of a school of brick architecture of which Toulouse was the center. One may prefer a stone architecture, but one cannot deny the lovely tones of brown and crimson madder acquired in time by these brick monuments of the Midi that seem created especially for resistance and long duration. Not the cathedral of Toulouse, but its monastic brick church of St. Sernin, is the supreme religious monument of the city and the grandest Romanesque edifice in France. Its date has been discussed by MM. de Lasteyrie, Corroyer, Saint-Paul, and Jules de Lahondès. In the last quarter of the XI century the monks began the choir of the present church, which combined the characteristics of the Romanesque schools of Burgundy and Auvergne. Those influences had passed south by way of Conques, where the abbatial of Ste. Foi had been rebuilt a generation before St. Sernin. In 1083 Cluny monks replaced at St. Sernin the canons regular, and where Cluny reformed, building activities usually followed. While the Toulouse monastery church was rising, its selfsame plan appeared in the northeast corner of Spain in the cathedral of Santiago Compostela, begun in 1082, too direct a copy to have been done by any but St. Sernin's own architect or his favorite pupil. In Spain the works went faster, so that Santiago Cathedral was completed long before the abbatial at Toulouse, and, being constructed in stone, its interior has not been marred by centuries of whitewashing. "The entry of Urban II into Toulouse" is pictured by Benjamin Constant in the Museum. In 1096, on his journey through France, preaching the First Crusade, he blessed the unfinished choir and transept of St. Sernin. The aisles around the transept form the most imposing part of the church. As the XI century closed, the transept was continued and the nave begun under the direction of a monk-builder, St. Raymond Gaynard, a man of wealth before entering the cloister. He conceived the masterly plan of five aisles. The side aisles were covered by a quarter-barrel vaulting that serves the purpose of a continuous flying buttress. Perhaps it was when the original architect of St. Sernin had proceeded to Santiago Compostela that St. Raymond became master-of-works at Toulouse. In 1119, a year after his death, another pontiff, Calixtus II, blessed St. Sernin.