EN
The author analysed woven fascines located under the northern piece of the defensive banks of the Poznan stronghold (registered at the 5 Posadzego site) and identified them as remains of hydro-technical infrastructure. The structures, similar to the contemporary timber frame structures, had the task of accumulating the material (sand) carried by the river along the line of the planned defensive banks. Similar structures had been discovered in the northern part of the 17 Ostrów Tumski site yet their function was not identified. The author also presents the chronology of the specific phases of the bank construction (based on the results of tree-ring-dating) and structure elements (pilots, starlings, the bank’s turn, stone founda¬tions). This is also an indication of an intended constructing the Poznan cathedral as the possible reason for extending the range of the fortifications around 980.