Virtutes Materiae: Cagliari, the City of Stone. Innovative Geo-tourist Itineraries Promoting the Use of Stone Resources Throughout Time

Abstract The historical urban development of the metropolitan city of Cagliari (Sardinia, Italy) relied heavily on the versatile use of locally sourced stone. The city’s extensive exploitation of natural resources is reflected in many settlements, such as the Phoenician-Punic necropolis of Tuvixeddu and the complex of ruins from Roman times Villa di Tigellio . Among the calcareous lithological formations of the Miocene succession, Pietra Forte stands out for its physical–mechanical characteristics and durability, which has allowed it to be used specifically for the construction of iconic monuments of the city's skyline, such as the Roman Amphitheater, the Pisan Towers, the Bastion of Saint Remy, the Basilica of Bonaria and the Cathedral of Santa Maria Assunta and Santa Cecilia , to name a few that are considered cultural heritages. Significant evidence of the great, millennial quarrying activity is Buoncammino, the Botanical Gardens, the pit of San Guglielmo, some “latomia”, underground quarries and so on. The evidence which has emerged between the subsoil and the built-up area may help develop a diverse and innovative tourism along with the cultural enrichment, which acknowledges the "geological history" of the Upper Miocene period as the result of the use of materials, which can be recognised in the most important city monuments, by its ivory colour range, which gives the city itself an evocative and elegant monumental structuring. A dedicated web application suggests a whole series of different geo-urban itineraries which would be customised to the visitor’s needs and developed as part of the project.