The Rock-Hewn Hypogea with Vertical Bell-Shaped Excavations and Constructed Vaults, in the Area of the Eighteenth-Century Quarries of Matera (Southern Italy)

The urban morphology of Matera, a UNESCO World Heritage site, is defined by a unique symbiotic relationship between the city and underground spaces carved into the rock. While much of the fame of the Sassi districts is based on the adaptation of natural karst cavities, a distinct type of underground space exists within the quarry areas, which left traces since at least 1660 on the slopes of the karst Murgia rising from the alluvial plain of the Gravina stream north of the city, near the Roman Appian Way. The specific phenomenon of underground spaces carved vertically into the rock, created not by the passive occupation and subsequent reshaping of pre-existing voids but by the active extraction of calcarenite blocks, is repeated several times in the quarry areas and, in fact, reflects the techniques of quarrying, in contrast to those of the settlement of the Sassi area. These structures, characterized by a bell-shaped profile and subsequently covered with vaults constructed from calcarenite blocks quarried from the same rock, represent a dual-purpose architectural strategy: the supply of building materials for the Baroque city and the simultaneous creation of underground spaces for quarrying related works, worship, and residential purposes. The distinctive feature lies in the excavation method: in this case, it is not identified any derivation from regularized pre-existing cavities for human use. Rather, the underground space is preferably constructed on compact and homogeneous benches, and any stratifications encountered during excavation do not influence the geometry of the excavation itself. they, at most, today constitute a theme of differential degradation and geo-structural behavior, and conservation. This construction method, therefore, stands in stark contrast to the horizontal adaptation of natural voids, regularized as described in the Giuffrè-Carocci “Code” and the Restucci Manual about traditional Matera’s “material culture”. The quarrymen began extraction from the surface, removing successive layers divided into “rows” and then into “blocks” of calcarenite. Each layer, equal in depth to the building block, traditionally a handbreadth high (about 24-26 cm), widens slightly compared to the previous one, with the characteristic “bell-shape” resulting from the inclination with which the “zuccotto” (a type of small pickaxe) was used to ensure maximum extraction volume and, in this case, optimal habitability of the resulting spaces. The chambers dug in this way presents sloping walls. This construction method is unique and deserves attention as it stands in stark contrast to the typical karst anthropization of the Apulian Murge, where irregular natural cavities were simply regularized and enlarged. The study concludes with a specific topic related to the reinterpretation of the traces identifiable on the residual surfaces of the excavation, within the underground structures. These can be primarily classified into two categories: signs of workmanship, left by traditional tools in vogue until the first half of the twentieth century, and signs of use, such as the creation of functional niches or wall recesses designed to accommodate special structures for the protection of the habitable spaces or their functional “furnishings,” or even significant signs: devotional, primarily in the form of crosses, inscriptions, or dedications.