ISPRA launches the National Database of Underground Cavities and Sinkholes. Between historical archives and machine learning models, a journey into the geo-archaeology of Italian cities
Beneath the polished paving stones of historic centres, below the asphalt of metropolitan arteries and the foundations of residential buildings, there extends a silent and invisible geography. It is Italy’s hypogeal territory: a dense, millennia-old network of voids made up of tunnels, abandoned tuff quarries, water supply cisterns, necropolises, sacred hypogea and military galleries.
This is a heritage of inestimable archaeological, historical and documentary value, yet one that also contains a potential threat. The interaction between these underground environments, the geological complexity of the soil and the increasing pressure of urbanisation generates a constant risk factor: sudden and devastating sinkholes capable of swallowing roads, damaging vital infrastructure and endangering public safety.
To address this insidious phenomenon and finally make the invisible visible and measurable, the Italian Institute for Environmental Protection and Research (ISPRA) has launched a systematic nationwide census and inventory. This has led to the creation of the National Database of Underground Cavities and Sinkholes in Italian urban centres, a strategic project designed to collect, harmonise and georeference an immense body of data that has until now remained fragmented.
The system integrates information drawn from historical archives, technical and cadastral maps, geological field surveys, photo interpretation and databases held by local authorities, translating it all into a homogeneous, interoperable and continuously updateable digital platform.
The pilot work focused on some of Italy’s most exposed and historically complex urban contexts.
Rome is undoubtedly the emblematic case. The capital rests on an immense underground network formed by centuries of extraction of building materials. To manage this critical condition, ISPRA has developed the Map of Underground Cavities in Rome, alongside an advanced susceptibility analysis model.
Using GIS systems and sophisticated machine learning algorithms, researchers cross-referenced predisposing variables — geology, cavity geometry and infrastructure networks — to identify in advance the areas most at risk of collapse.
Another key stage of the research concerns Naples. Here, intense excavation of tuff deposits has created a true mirror metropolis beneath the ground. In close collaboration with the University of Naples Federico II, ISPRA has structured an extremely detailed database, subsequently expanded and validated thanks to the resources of the GeoSciences IR project, funded by the European Commission through NextGenerationEU within Italy’s National Recovery and Resilience Plan.
The same model of cooperation with the Neapolitan university has also been successfully applied in Palermo, whose geological configuration, linked to the extraction of calcarenite, makes the prevention of ground collapse an absolute priority for the protection of citizens and historic buildings.
The contexts analysed reveal an exceptional geological variety, demonstrating the adaptability of ISPRA’s methodology. In Cagliari, the mapping process produced the city’s first systematic census, geolocating 205 sinkhole events and outlining 195 cavities excavated over time for extraction, military and civil purposes.
In Trieste, meanwhile, the scientific challenge concerned the interaction between the complex natural karst matrix typical of the Julian territory and the underground structures created by humans, in a study carried out jointly with the University of Trieste.
The project also shows particular sensitivity towards the provincial dimension and smaller towns, which often preserve unpredictable fragilities. Collaboration with the University of Tuscia made it possible to map the subsoil of Viterbo, excavated in pyroclastic and tuff deposits of volcanic origin, and the Rieti plain, characterised by complex alluvial and carbonate dynamics.
The same academic synergy extended to the historic towns of Lazio, leading to in-depth investigations in the territories of Bolsena, Grotte di Castro, Montefiascone, Ardea and Cittaducale.
The National Database represents a genuine methodological turning point for territorial governance. It is not only a monumental archive of urban geo-archaeology, but also a modern decision-making tool for public administrations, geologists, urban planners and Civil Protection operators.
Moving from an emergency-led logic to a knowledge-based culture of prevention makes it possible to plan targeted consolidation, monitoring and maintenance interventions on technological networks before the underground void demands its price. Italy is thus beginning to protect its future by starting precisely from the most hidden memory of its past.
Cover image: Sinkholes © ISPRA
