 The first historically recorded Bishop of Ampurias, Bono, had a part around 1100 in the foundation of the monastery of San Nicolò di Solio, one of many founded in the diocese by the Cassinese Benedictine Congregation in the 11th and 12th centuries, thirteen of which depended on Santa Maria di Tergu; whether their possessions ware exempt from the episcopal authority remained a matter of continuous dispute, giving to several papal interventions in favor of the Benedictines, possibly culminating in the murder of the abbot of Santa Maria di Tergu shortly before 1203.According to the "Rationes decimarum" (mid 14th century), the diocese comprised 21 "plebanies' and rectories (parishes).The town of Ampurias faded with its port due to the sand-clogged bay of Coghinas, so in the 14th century the episcopal see was effectively transferred (without title change) to Castelgenovese (now Castelsardo), formalized in 1503 when Pope Julius II elevated the Benedectine priory of Sant'Antonio into the new diocesan cathedral, which presently remains co-cathedral in the successor bishopric.