Many sculptors of the Fabbrica del Duomo actively participated in the construction of the building.

The Court of Honour, as well as the front, it is of particular value; here an ambitious decorative program was carried out on two main themes: the exaltation of the hero through the narrative of the labors of Hercules (in the lower register) and the exaltation of the power of the love in its various degrees, through images (in the register top) taken from the "Metamorphoses" by Ovidio
Inside the Hall Alessi, with paintings and stucco work, we report the presence of four bas-reliefs above the windows: their issues are at dawn, day, dusk and night. On the sides along the roof, and that is the side windows in back position, there are four large bas-reliefs symbolizing air, earth, water and fire.