Resumen
The National Museum of Rome has an important collection of Mithraic sculptures found in the years 1973?1975 during the archaeological excavation under the early Christian basilica of Santo Stefano Rotondo on the Caelian hill in Rome. The sculptures excavated from this Mithraeum show many traces of gilding and polychromy, whose best example is the great bas-relief with Mithras slaying the bull discussed in this work. The analysis was conducted during a scientific campaign in the museum with portable instrumentation of the Institute for Conservation and Valorisation of Cultural Heritage, ICVBC mobile laboratory following a completely non-invasive approach. By means of a protocol based on the use of multispectral imaging, microscopy, X-ray fluorescence (XRF) and fiber optic reflectance spectroscopy (FORS), this study allowed to better understand the technique used and to make comparisons with other representations of Mithras slaying the bull.