Archaeological landscape in central northern Istria (Croatia) revealed by airborne LiDAR: from prehistoric sites to Roman centuriation

This paper presents the results of a research aimed at investigating by airborne LiDAR the ancient landscape of a sector of central northern Istria (Croatia) from prehistory to Roman times. The area, approximately corresponding to the territory of Oprtalj/Portole, is located in a strategic position just north of the mid–Mirna/Quieto river, an important waterway connecting coastal Istria with the inlands since prehistory. The elaboration of high-definition LiDAR data compared with aerial and satellite images, historical cartography and field surveys allowed us to identify unreported prehistoric and Roman features and also get detailed topographic information about already known sites. Beside a few protohistoric hill forts discovered in the past, an open-air Neolithic or Copper Age site, a probable Bronze Age burial mound and three small protohistoric fortifications have been identified. These hill forts are clustered around a north-south valley, which represents a preferential access route from the larger Mirna valley to the karst plateau north of Oprtalj/Portole. In the same plateau, small Roman buildings associated with enclosures and probable artificial ponds have been interpreted as remains of farmsteads related to small-scale herding and agricultural activities. In the southern sector of the investigated area, consisting of marls, sandstones and fertile soils, large scatters of archaeological materials sometimes associated to outcropping features are probably the remains of larger structures characterized by a well-developed agricultural economy. Particularly interesting is the identification of fossil rectilinear land division features that overlap with the cardines of Istrian centuriation. Before our study, centuriation was identified only in the territories of Poreč/Parenzo and Pula/Pola, hence believed not to extend beyond the Mirna river. The new evidence revealed by LiDAR and satellite images, however, shows that a large part of central and northern Istria, between the Mirna and the Dragonja rivers, was divided by the same grid. Based on these considerations, the archaeological evidence here presented makes the Istrian peninsula one of the largest areas in the entire Roman world to have undergone a single planned land division survey.