 The interior is basilica shaped with three aisles separated by two rows of columns, the latest octagonal, as a result of the 16th century enlargement.Behind the altar is the grand polyptych created by the painter Giovanni Canavesio in January 1500, four meters high it includes 38 compartments framed with wood covered in gold these paintings attempt to capture the humble humanity of the story of Jesus, with an expressionism previously unknown in medieval art demonstrating the upcoming Renaissance style.They show Canavesios taste for theatrical and dramatic situations.