Notre Dame-du-Port is a masterpiece of the Romanesque school of Auvergne.[209] When it was built lava stone was not in use for construction, but solely for decorative purposes. So curiously alike are all the pre-Gothic churches in this province that one architect might have planned them. The venerable crypt of Notre Dame-du-Port was built in the XI century. The Romanesque church above it was constructed during the XII century and has all the Auvergnese traits: a central tower in two stories set on a barlong which forms a kind of upper transept, a compact apse with snug absidioles whose exterior walls are decorated by colored volcanic stones in marquetry designs, a western narthex, and a principal span covered by a half-barrel vault undivided by transverse arches and buttressed by side aisles surmounted by tribunes, which meant that light entered the middle vessel indirectly. Auvergne, like Burgundy, attempted to light her upper church by a clearstory, but found the experiment hazardous and gave it up. Her churches have stood intact through centuries of harsh winters. The very mortar lines were made means of decoration; wide bands of red mortar were found to be effective with blocks of black lava.[210] In the volcanic soil of Auvergne were elements that rendered mortar as resistant as stone. The local Gallo-Romans had used the polychrome lava as decoration. The interior apse of Notre Dame-du-Port is a gem of masoncraft. Around the tiny processional path stand engaged pillars that are decoration and buttresses, too. The regional skill in sculpture appears in the capitals of the main piers, where the story is related with animation, even if the figures are too squat and the heads too large. The armor indicates that the work was done early in the XII century. The doorjamb images at the southern entrance of the transept were sculptured in the years when St. Thomas Becket came to Clermont wearing the white robe of the Cistercians who had given him hospitality in France. Crowds gathered every day to receive his blessing, for all Christendom held him to be a saint defending right and liberty. A cast of Clermont's archaic portal, whose charm is exceptional, with its seraphim of the mystic triple wings, has been placed in the Trocadéro Museum at Paris. When this side entrance was completed, Richard Coeur-de-Lion was making over his claims in Auvergne to his lifetime rival, Philippe-Auguste, which cession was to lead, in time, to the erection of the Ile-de-France Picardy cathedral of Clermont.