The Cathedral was for John Bosco favorite among the many churches in the city. Here, a student, he went every morning and evening to pray to Our Lady of Grace, and, amongst these walls, prepared for the Latin course the clerk Charles Palazzolo, who wanted to become a priest. During his seminary years he continued to attend the Cathedral for the functions and the catechism to young people, while at the altar of the Madonna delle Grazie, 9 June 1841, when Don Bosco will be celebrating its fourth set.