On the south side of the Cathedral, near the façade, residents and visitors may notice some scaffolding, signs that work on the flying buttresses continues.
The flying buttresses, considered by Viollet-le-Duc to be “the most forthright and energetic expression" of medieval cathedrals, are generally built to contrast the outward force of the vaulted oval ceilings of the nave. Those located on the southern side of the Duomo do not have a purely static function, but rather respond to the coherence of the design and serve to channel rain water run-off directly from the roofs to the gargoyles.
Work is currently being done to buttresses AR1, AR2, and ar1, thus labelled according to the structural code used by the Veneranda Fabbrica, in which upper case initials correspond to architectural elements at higher elevations and lower case initials correspond to those at lower elevations.
Most of the flying buttresses located on the southern side were put in place over the course of the 19th century, but the Fabbrica had already determined their appearance in the 15th century.