The search for an ancient viking harbour with GPR

In the region near Hollingstedt (Schleswig-Holstein, North of F.R.G.) the ancient viking transit habour on the trade-way between the North Sea esp. Dorestad (Rhin area) through Haithabu and the Baltic Sea esp. Birka (Sweden) is probably located. Employing only pure historical means often fails in getting unequivocal information about the change of ancient settlements in time and space. Because changes of settlement- centres like-Hollingstedt and Haithabu have often been a consequence of displacements of harbours, the knowledge of their locatiori is a key for the understanding of the past.