 One of the "libri pontificales" records that the Syrian Pope Gregory III (731–741) had performed a major expansion of the church in the early 700s, which had been up until then a small oratory.It was, however, apparently already in bad condition by the pontificate of Pope Adrian I (772–795), who rebuilt it.An anonymous pilgrim of Einsiedeln, writing in the same century, refers to it as "S. Sergii, ibi umbilicum" ("[the church] of Saint Sergius, near the "umbilicus").