A superficial examination of the subject of my communication could suggest that the limitation of my research field to the cistercian abbayes of Western Germany is a way of harmonising with the current border of the two Germans. This is definitely not the case. The cistercian monasteries, to the west of a Elbe-Saale line (so that my definition must actually be clarified) are really different in the Middle Ages and on many points from those in the Al area...