Dal rilievo alla ricostruzione del progetto: la torre Pisana nel Palazzo Reale di Palermo

The paper focuses the survey and representation of the Pisana Tower in the Royal Palace of Palermo. The tower, which has recently been inserted in the UNESCO World Heritage List, was built in the XII century under the patronage of Norman kings. Along the centuries, the tower has undergone several transformations, to fit ever-changing uses. The coexistence of such heterogeneous elements, combined with the fragmentation of the passages connecting the levels of the tower, conceal the original unity and the typology of this historical building. Researches focusing the study of monuments deeply transformed along their history, even when based on the cooperation of multidisciplinary scholarships, rarely reach a critical synthesis. Representation, if intended as something more than ‘visualization’, is the conceptual tool capable of operating the connection between information data (surveys, historical researches, diagnostics) and the physical layout of the building, as well as the detection of the relations between apparently disconnected parts. The Pisana tower has been surveyed with a laser scanner; topographic survey has strongly supported the registration of point clouds, which often had no areas of superimposition, due to the vertical layout of the tower. The process of interpretation of metric data has allowed the connection of information from documentary sources and the present layout of the tower; such connection supported both the attribution of the parts to a specific historical period and the validation of historical documents and drawings. The research aims to give evidence of the role that surveying and representation play in the interpretation of historical monuments deeply modified along their history, an occurrence that is quite usual in the Mediterranean area. The process of representation and 3D modeling has led to a deeper understanding of the relations between the visible and hidden parts, and of the geometric proportions underlying the design of the tower.