Today's Sanctuary of Santa Maria del Monte is the result of several changes from the 12th century to the present day. The first Romanesque project of the church had a single nave. In the mid-15th century, the sanctuary was enlarged with two side aisles by the Duke of Milan Galeazzo Maria Sforza. Finally, in the 17th century, all the paintings and decorations were renewed, including the imposing altar with the 14th-century wooden statue of the Black Madonna.
The sanctuary is closely connected to the cloistered monastery: in the middle of the nave, above the arch, you can see the gratings from which the nuns may follow the religious celebrations without breaking the seclusion rule.