Ghost centuriation of Roman Istria: new evidence from lidar survey

This study presents new evidence of Roman centuriation in northern Istria (Croatia), a region previously considered devoid of such land division systems. While the centuriation grid of southern Istria—linked to the Roman colonies of Pola (Pula) and Parentium (Poreč)—have been documented since the 19th century, its northern extent remained unexplored until now. Using the Croatian national lidar data (2022–2023), we identified fossilized traces of Roman limites (cadastral boundaries) in the form of micro-reliefs (low embankments) and, primarily preserved in overgrown or forested areas. These features align with the 20 × 20 actus module (≈707 m) and NNE–SSW orientation characteristic of Istrian centuriation, confirming the grid’s extension across the 80 km of the western Istrian coast. This discovery shows that centuriation was not limited to Istrian administrative boundaries as previously thought. Instead, it suggests a unified survey campaign across the peninsula. Unlike the south of the peninsula, where Roman boundaries still shape present-day field systems, traces in northern Istria are abandoned or "ghost" features, invisible without high-resolution topographic methods (lidar data and appropriate algorithms, in this case TPI and Toposhade). The study underscores the role of geology and taphonomy in preserving—or erasing—ancient landscapes, while demonstrating lidar’s potential to revisit "invisible" archaeological features. Future research may further revise Istria’s centuriation extent by targeting overgrown areas and subtle ploughsoil anomalies.