The mud layer of the Haddebyer Noor, a lake in front of the old Viking settlement Haithabu near Schleswig, has been investigated with a recently developed device for high-precision seismic reflection, with the intention of detecting archaeological objects. This delivered the locations of a number of wooden and metallic objects. Some of the tus mapped objects were regained by diving operations. Others, like wooden harbor constructions of unexpectedly large dimensions, and a large (second) shipwreck were left conserved in the mud. The conclusion drawn from this investigation is that the inhibitants of the old Viking settlement had a far higher stage of development than hitherto suspected. -- AATA