Around 1100, the counts of Leuven and Brussels left the bottom of the valley of the Senne and built their castle on the heights of the Coudenberg from where they could dominate Brussels. With the creation of the Duchy of Brabant in 1183 by the German Emperor Frederik Barbarossa, the Coudenberg gained in importance and was included within the first great wall built around the city. The hunting park of the dukes led down the hill to the north, a remnant of which is now Brussels' Park.