After the borders of the Roman Empire were drawn back to the Rhine boundary in the 3rd century BC, the Alemanni gradually settled on the north shore of Lake Constance and, later, on the south bank as well. After the introduction of Christianity, the cultural significance of the region grew as a result of the founding of Reichenau Abbey and the Bishopric of Constance. Under the rule of the Hohenstaufens, Imperial Diets ("Reichstage") were held by Lake Constance. In Constance, too, a treaty was drawn up between the Hohenstaufen emperor and the Lombard League. Lake Constance also played an important role as a trading post for goods being traded between German and Italian states.