Three lines of ditches and embankments and inside a void: Results of Archaeological Research at the Early Iron Age Site in Kościuki (Podlaskie Voivodeship, North-Eastern Poland)

Airborne LiDAR surveys have identified 27 Late Bronze and Early Iron Age fortified sites in the valleys of the Biebrza and Narew rivers in northern Podlasie, sharing similar locations, forms, and dimensions. In 2019, interdisciplinary geomagnetic and ground-penetrating radar (GPR) surveys, followed by excavations, were carried out on the site in Kościuki (Białystok district).The site lies on a sandy elevation near a peat bog and consists of three concentric embankments and ditches about 100 m in diameter, enclosing a central area of only 20 m. Excavations revealed traces of palisade-topped ramparts and well-preserved wooden elements between the ramparts. Radiocarbon dates of the timbers indicate construction between the 7th and late 5th centuries BC. No structural remains or artefacts indicating habitation were found within the enclosure, only a few ceramic sherds in the ditch fills. The monumental scale and inward-sloping palisades suggest a non-defensive role, perhaps as a permanent ritual or ceremonial centre rather than a military fortification.