Where were the boundaries of the diocese? We do not know. What of its strength? The names of other bishops of Urgell who signed councils and synods are on record: Simplicius (Toledo 589, Zaragoza, 592 and Barcelona, 599), Ranarius (Toledo 633), and Maurellus (Toledo 653 and 655), for example. And how did it fare during the years of Saracen invasion from 711 to 725? The diocese of Urgell, thanks no doubt to its geographical location, was the only one in Catalonia to survive and to maintain an uninterrupted line of incumbents together with its organisation and former institutions. In 731 Bishop Nambad was burned at the stake in Llívia at the orders of the Muslim chief Munussa (of Narbonne?), and from 781 to 799 Bishop Felix, a famous person in the history of the church, presided over the local community. His adoptive theses, according to which Jesus was the Son of God only in the sense of an adopted son, brought him into confrontation with the theologians of the Imperial Carolingian court. The controversy was a rowdy one and Bishop Felix, stripped of his office and driven into exile, died in Lyon, possibly in 811. It was then, in 793, that the Muslim chief Abd-el-Malik failed in his attempt to besiege Narbonne and fell back along the Segre Valley. As he passed through, he destroyed the episcopal city of Orgellia (Castellciutat) and its Visigothic cathedral. Once the Saracens had departed, the Frankish Emperor Louis the Pious had the city and the cathedral rebuilt. That was the crucial moment in the formation of two centres of population: the Civitas Orgellia on the banks of the Valira and the Vicus Orgelli, two kilometres beyond by the Segre. There may already have been some houses there in the valley, but the new city was organised around the new church, Santa Maria. This was the nucleus of the present La Seu d'Urgell. From that time the city grew and became established, not only as the centre of a wealthy region, but also as the head of a large diocese along the Pyrenees which lived an intense Christian faith.