 Unlike the other Rhenish dioceses — Mainz and Cologne, Trier was the former Roman provincial capital of Augusta Treverorum.Given its status, Trier has always been the seat of a bishop since Roman times, one of the oldest dioceses in all of Germany.The diocese was elevated to an Archdiocese in the time of Charlemagne and was the metropolitan for the dioceses of Metz, Toul, and Verdun.