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Cologne is the oldest of the German bishoprics after Trier. Maternus was the first bishop of Cologne whose name has come down to us. It has been documented that in 313 Emperor Constantine the Great summoned him to a synod in Rome, and that he took part in the Synod of Arles in 314. So we know that the Christian community in Cologne was already significant enough to be presided over by a bishop. Maternus was venerated as a saint. He is remembered in many pictorial representations in the Cathedral and other Cologne churches.