Admiring the Duomo's apse, one cannot help but be struck by the giant window panes, enclosed by the equally grandiose and majestic window frames. The one in the middle, in particular, is certainly the most well known, also called the window of the raza, due to the Visconti-esque symbol positioned in the centre of the rose.
It is to this "finestrone della raza" that this drawing refers. It is a sketch by Paolo Cesa Bianchi, an architect for the Veneranda Fabbrica, for the presentation of a restoration project in July 1883. The drawing is attached to a report in which interesting construction details and references to past restorations emerge. The ancient marble used to build the architectural structure is, according to an examination by the architect, still perfectly healthy, "as much in its more delicate parts as in its more voluminous ones. The marble is of excellent quality, making it possible to sculpt it as though it were new."
The architect goes on to emphasise the importance of the “techniques that the Duomo's high art and experience have taught its technicians", skills which now, as then, make it possible to preserve many of the Cathedral's architectural and decorative elements.