sentences:  Just to the west of the original church, he began building a new structure with two towers, and then, from 1140 to 1144, he began to reconstruct the old church.Most of his modifications were traditional, but he made one remarkable innovation; he decided to create a new choir at the east end of the building, using the pointed arch and the rib vault in the construction of the choir and the ambulatory with radiating chapels.The use of rib vaults, and buttresses outside supporting the walls, allowed the elimination of the traditional walls between the chapels, and the installation of large stained glass windows.