The origins of the first structure are obscure and shrouded in legend. There was a 9th-century church with bishop's palace at the present location. In December 1058 a synod was held in this church resulting in the election of pope Nicholas II and the deposition of the antipope Benedict X.In 1196, the cathedral masons’ guild, the Opera di Santa Maria, was put in charge of the construction of a new cathedral. Works were started with the north - south transept and it was planned to add the main, larger body of the cathedral later, but this enlargement was never accomplished.By 1215 there were already daily masses said in the new church.