Main church of a diocese: the church where you find the bishop's see. In the early Christian cathedrals, the bishop's see was standing in an apse of the choir (called (exedra), but nowadays it stands on the side in the choir. In the early middle ages, the abbey churches were larger and had more power than the cathedrals. The more power the cities (12th century and later) were getting, the more those cities replaced their old churches by new, giant gothic cathedrals. Cathedrals, town halls and bellfries became thé symbols to show their power.