In the 12th century, Abbot Suger of Saint-Denis had the chevet of the basilica rebuilt to let light in. His intentions were religious: he demanded that the stained glass windows be readable from the bottom to the top so that the eye could look up to the sky. This was a very expensive innovation for Suger, as the cost of manufacturing them exceeded the entire cost of construction. In the 13th century, a rose with coloured stained glass was created at each end of the transept. The northern rose (photo) bears in its centre the image of God and at noon, that of the Virgin Mary. The stained glass windows of the triforium tell the life of the popes.