Pope Callixtus II
Both Aribo and Poto were mentioned as founders ("fundator huius ecclesie") in a 13th-century parish register. Though the foundation legend of a Carantanian duke Domitian has not been conclusively established (see below), a church may have already existed at the site since the days of Charlemagne. The monastery had definitely been established before 1122, when it was mentioned in a deed issued by Pope Callixtus II.