This study concerns the Franciscan monastery, situated in the historic centre of Cagliari (Sardinia, Italy). It was founded in the 13th century, and transformed up to the present day. Its historical-stratigraphical complexity and the lack of data about its evolution led us to carry out an interdisciplinary inquiry. The investigation began with the use of a laser scanner survey aimed at defining a chronological hypothesis applied to the building which was based on reconstruction of historical maps, examination of masonry techniques and stratigraphic analyses. The dating obtained led to the choice of masonry samples to compare with other local and contemporary buildings where the chronology is well-known with the aim of confirming previous hypothesis. Analysis of the masonry samples allowed an understanding of their actual structure and composition, with reference to specific historical events. The mineralogical-petrographic characterization of building materials was essential. Plaster and mortar have been studied with instrumental techniques (OM, X-Ray diffraction) to analyze their components. The data obtained lead to a better knowledge of the Franciscan complex and this is essential for a restoration project respecting all its historical signs. The data is also very useful for dating other local buildings characterized by the same masonry techniques
