Sulle tracce del perduto mosaico della cupola di San Saturnino di Cagliari. Fonti seicentesche e dati materiali

The basilica of San Saturnino in Cagliari, one of the most significant medieval monuments in Sardinia, still preserves traces of a complex architectural and decorative history that began in the Byzantine period and led to a progressive decline in the late Middle Ages. Among the lost elements, particular interest lies in the mosaic that originally adorned the dome, known exclusively through modern written sources. Seventeenth-century accounts, especially those of chroniclers and travelers, provide valuable clues that allow hypotheses to be formulated regarding the mosaic decoration of the domed structure at the center of the basilica, a symbolic and identity-defining building for the Christian community of Cagliari. This study aims to combine the analysis of these sources with the examination of the material evidence still visible in the building. Direct observation of the masonry structures and the inner surface of the dome makes it possible to put forward considerations on the methods of application of the mosaic, as well as on its possible phases of renewal or loss. Comparison with other contemporary contexts in the Mediterranean contributes to outlining—albeit through indirect evidence—the technical and decorative choices that characterized the work, placing it within a broader framework of Byzantine and medieval artistic practices. By intersecting documentary sources and material evidence, this paper seeks to propose a broader methodological reflection on the theme of memory and the transmission of lost works. In this sense, the case of the dome of San Saturnino represents a privileged observatory for understanding the dynamics of conservation, transformation, and loss of Sardinia’s monumental heritage, and for highlighting the role of written testimony and surviving traces in the reconstruction of an artistic and cultural landscape that has been largely erased.