A computer simulation in a GIS-based environment is used by the author to present a reconstruction attempt of the early medieval settlement area in the Maskawa Valley, Central Poland. Archaeological and historical data, including data from the early medieval stronghold from Giecz constitute the basis onto which habitat zones will be delineated in relationship to the geomorphology, including the climate conditions, and the hydrological system with its catchment areas within the Valley. The reconstitution of primeval forest and the vegetation extent as well as the biotop matrices will be in a large measure based on the existing research results carried out at various Polish institutions. The conclusion will highlight the relationship between groundwater and surface water as the main factor in the selection of habitat zones, including the location of early medieval strongholds.