The Wittelsbachs (a German/Bavarian dynastic and European royal family) were the first to expand and fortify the settlement. In that way they controlled the passage of the important commercial salt route over the Traun, from Bad Reichenhall to Munich at the border of the "Erzstift Salzburg" (the archbishopric of Salzburg). In the year 1120 the lords of "Truna" settled in the current urban area because of its favourable strategic position. They built the castle at the border of the city plateau, which is surrounded by the River Traun as well as its close proximity to the main route of commerce.