The conservation of the Duomo is an activity that will never end, and that requires continuous intervention on the monument. The centuries-old duration of the construction of the Cathedral entailed from the beginning problems of maintaining the parts built and already damaged. The first application of the modern conscience of restoration was the consolidation of the Spire Maggiore which the architect of the Fabbrica, Pietro Pestagalli (1840), had proposed to demolish and rebuild on his new project more in keeping with the style of the cathedral. Since then the work of the yard on the built but damaged parts has continued trying to respect the pre-existing structures. Since then, countless interventions have been held to combat the state of decay of which the sculptures and ornate works were affected by smog and pigeon droppings. For this reason, the cathedral is jokingly defined as "an open construction site". Even inside, the works have never stopped and Magistri had the honor of restoring one of the oldest masterpieces in the cathedral, namely the Gothic portal of the Aquilonare Sacristy, in addition to the adjacent North transept and the counter-façade.