Stone materials used for monumental buildings in the historical centre of Turin (NW Italy): architectonical survey and petrographic characterization of Via Roma

One of the peculiarities of Turin (NW Italy) lies on the presence of monumental arcades which mainly consist of stone material. These arcades, characterized by more than 12 km of interconnected paths, represent one of the widest city promenades of Europe and are an architectural, aesthetic and socio-economic example unique in the world. This paper, analysing the urban axis of Via Roma (Rome Street), aims to study the material used in arcade construction. The main stones occurring in Via Roma have been identified and described from a petrographic and mineralogical point of view in order to find out the corresponding geological units and original quarry sites. The minero-petrographic study is accompanied by an architectural survey that was performed applying different methods, as well as the geometric mapping and the perspective rectification of span-types, of block terminations and of other architectonical elements, in plan and in elevation, of the arcades. This allows us to emphasize the merging of cultural and scientific interest for the stone materials used in the historical architecture of a town closely interconnected to the surrounding Western Alps orogenic chain.