Geometry, drawing and design between theory and art of fortifying. Comparison between the 'regular fortress' in the Trattato di Fortificatione by Guarino Guarini and the Citadel of Turin by Francesco Paciotto

In Guarini's theoretical speculation and building practice, disciplines as geometry, drawing and design were closely interrelated, as mainly demonstrated in the treatise Architettura Civile and in his civil and religious buildings. These concepts seem also central in his other writings about the art of building, including the Trattato di Fortificatione (1676), one of his lesser known works. The author of this paper who, on several occasions, has studied the relationship between geometry and design in Guarini's work, presents today a study, culminating in the drawing of a geometric deconstruction concerning the 'regular fortress', a graphic scheme drawn by Guarini in the Trattato di Fortificatione. The identified sequence of linked figures enabled to define the nomenclature of the elements described in the text, discovering a partial geometric correspondence between such scheme and several representations of the Citadel of Turin. The Citadel was designed by Francesco Paciotto and built between 1564 and 1577 and then gradually dismantled from the mid Nineteenth century. The research proposed in the present paper deepens, thanks to geometric and graphical analyses, the comparison between Guarini's scheme and the Citadel, a no longer existing place about which many drawings and reconstructions are preserved , not always fully consistent with each other.