The Benedictine Basilica of S. Angelo in Formis (Southern Italy): a therapy without diagnosis?

The Benedictine Basilica of S. Angelo in Formis was founded in the XI century by the Abbot Desiderio, over the ruin of a Roman temple dating back to the V century BC. It contains an outstanding cycle of frescoes with stories of Old and New Testament, probably the most important document of the medieval painting in Southern Italy. It is known that some repair works have been carried out in XVIII century; in 1930 an earthquake produced the collapse of the roof, reconstructed soon after. Starting in 1969 some fissures ap-peared in the central nave and gradually opened and extended to other parts of the Basilica. Following re-peated alarms on the safety of the Basilica, geological survey of the area, subsoil investigations and geodetic monitoring of a number of points both inside the Basilica and outside have been carried out till present. The paper reports the results of these investigations, that confirm the occurrence of differential settlement of the monument. The attempts of interpretation of the observed movements and the possible interventions are discussed.