While the piazza was originally created in the 14th century and has been gradually developing ever since (along with the Duomo, that took about six centuries to complete), its overall plan, in its current form, is largely due to architect Giuseppe Mengoni, and dates back to the second half of the 19th century.
Kuigi väljak rajati 14. sajandil ja see on sellest ajast alates järk-järgult edasi arenenud (koos toomkirikuga, mille valmimine võttis umbes kuus sajandit), tekkis selle üldine plaan tänapäevasel kujul tänu arhitekt Giuseppe Mengonile ja see pärineb 19. sajandi teisest poolest.