The building was constructed over a period of 25 years and has three naves that rise (the central one is as high as a 12-story building). Compared to the previous period, the cross vault was replaced by an ogival vault and the round arch by a pointed one: in this way, the structure became higher and higher. In place of the exterior walls, 176 stained glass windows, with a total surface area of more than 2600 square meters, let the light pass through, penetrate the space and become the protagonist.

The windows tell biblical stories and events and replace the frescoes of Romanesque churches. Famous for the intensity of their blue color, they were made by adding cobalt to the glass mixture.