Duchy of Silesia
Duke Mieszko III the Old at first ruled over the western part of the Greater Polish lands at Poznań. His dominion bordered on the Polish Duchy of Silesia in the south, on the Seniorate Province in the east and on the Pomeranian lands in the north. In the west the Greater Polish lands stretched up to Lubusz Land on the western Polish border, where in 1157 the Ascanian count Albert the Bear established the Imperial Margraviate of Brandenburg.