Hrolf Ganger, better known as Rollo the Walker, was born in Norway around 845. Banished, he takes the lead of a group of vikings which attacks in particular the coasts of the English Channel. It goes up the Seine several times to Rouen and Paris (886). In 911, by the treaty of Saint-Clair-sur-Epte, Charles III the Simple gave him part of Neustria, mainly the county of Rouen, the base of the future Normandy. In exchange, Rollo undertakes to prevent the other Viking bands from going up the Seine. He was baptized in the cathedral of Rouen under the first name of Robert. The descendants of Rollo are called the Rollonids. From Rollo came most of the European royal families. Rollo is indeed the ancestor of William the Conqueror (King of England).
In the middle of the 12th century, the duke, who came from the south, expands his power in the north. In 1142 he took over Braunschweig. In 1195 he died in his residence city of Brunswick. Not only in front of Dankwarderode Castle in Braunschweig, but also in front of the cathedral churches in Lübe