The four windows that survived the fire of 1194 which destroyed the old cathedral are superb examples of Romanesque art and regarded as one of the wonders of Chartres. The most famous of these, the Beautiful Window, is a glorification of the Virgin Mary, seated on the Throne of Wisdom. Painted in the mid-12th century, after the fire it was placed at the entrance of the sanctuary to identify Mary as the Gate of Heaven. It was restored in 1906 by the glass artist Gaudin, who changed the drapery of her robe and replaced her head, giving it the slight tilt we see today. In the Romanesque period she would have held a strictly hieratic pose appropriate to figures of majesty. For the Virgin’s tunic, of which the extremely precious relic had been kept at the cathedral since the 9th century, the Romanesque artists chose a glass of very pale blue. Lightened by numerous air bubbles to imbue it with a celestial luminosity, this blue brought Chartres universal fame. The three other Romanesque windows, in the western façade, feature depictions of Christ. The announcement of his advent in the Old Testament is shown in the theme of the Tree of Jesse, as it is in the Abbey Church of St Denis. The centre window shows the Life of Christ from the Annunciation to his entry into Jerusalem, leading to the Majesty of the Virgin, thereby emphasising the Incarnation on this façade. Lastly, the Passion, brought vividly to life using warm, deep colours, completes the narrative by telling the story of the Resurrection of the Pilgrims of Emmaus.
A second phase of window installation, the main one, began after the fire of 1194. This work took place during the first third of the 13th century. Installation began with the lower windows in the nave, shortly before 1200, followed by the windows in the ambulatory and radiating chapels, which are thought to have been glazed during the first ten years of the 13th century. Later, the upper windows of the choir were installed, followed by the rest of the windows in the ambulatory before 1220. Next came the upper windows in the transept, starting with the windows in the south arm, which probably date from 1226 to 1230 during the regency of Blanche of Castile, followed by the windows in the north facade, which have been dated to around 1230-1235.
In the mid-13th century it was decided that the cathedral was too dark, so the decision was taken to replace some of the historiated stained-glass windows in the ambulatory with clear windows. In 1328 a canon, Guillaume Thierry, donated a grisaille window that made use of the new silver-stain colouring techniques invented around that time. A new phase of window installation began when the Chapel of St Piatus was built on the east end of the cathedral in around 1350. These windows feature large figures of the saints pictured individually under the canopies. In the late Middle Ages another stunning work was added to the cathedral in 1415 when the Vendôme Chapel was built in the sophisticated flamboyant architectural style on the south aisle of the cathedral. Since then the windows have been continually maintained, restored and complemented to the present day.