If you visit the Duomo on a sunny day it's impossible not to be dazzled by the splendour of the Cathedral's stained glass windows as the sunlight filters through the thousands of glass panes, colouring and illuminating the monument.
The Grande Museo del Duomo preserves and displays several stained glass windows, both old and modern, dating from the 1400s to the 1800s. Over the centuries stained glass techniques have undergone various changes, and between the oldest and the newest there are many differences, not only in the "design", or rather in the preparation of the sketches, but also in the creation, use, and positioning of the glass planes.
Of the many on display, two in particular capture, in a certain sense, the history, or rather the histories, of the Cathedral's windows: a large Angel in prayer and an Angel with mirror, both from the 19th century. The backgrounds of these two great figures is enlivened by multiple coloured panes, a fragmentary testament of much older windows that have long since disappeared:plant, architectural, and drapery motifs, as well as more clearly distinguishable elements like faces, angels, and weapons. Using the original panes dating from the 15th and 16th centuries, the Fratelli Bertini workshop integrated the two angels in the last quarter of the 19th century. Close and contemporary observation of the panes allows us to admire, at first glance, the evolution of the enamels, strokes, and design, as well as of the glass workmanship, helping us to imagine, if only through the power of suggestion, the light that has illuminated the Duomo throughout the centuries.