sentences:  During the rule of the first monarchs of the Piast dynasty, even prior to the Baptism of Poland, Płock served as one of the monarchial seats, including that of Prince Mieszko I and King Bolesław I the Brave.The king built the original fortifications on Cathedral Hill (), overlooking the Vistula River.From 1037 to 1047, Płock was capital of the independent Mazovian state of Miecław.