Built in 524 AD, it preserves inside few plastered surfaces due to its complex history which, after a long period of disuse, culminated in the collapse of the south aisle (1877). Its saving in 1900 made it possible to save, in the first three bays of the left aisle the only plastered and painted surfaces. The cross vaults in brick masonry are coated with a light coloured plaster in lime mortar, containing small and medium sized aggregates and are painted with dry grotesque motifs. The 16th century decorations on the two vaults highlight executive diversities and replace a previous phase whose traces are outlined by tiny oldest pieces of fresco that emerged during the cleaning operations.

The poor state of preservation of the painted plaster was related to a protracted situation of meteoric water infiltration from the coating and a general lack of maintenance that caused large quantities of soluble salts and products resulting from the decomposition of organic materials. Moreover, previous interventions have placed foreign substances incompatible with the original material which led to an additional deterioration of the painted plasters stability. Our intervention, besides the conventional cleaning methods, used products with high biotechnological content, while we adopted nanophysical systems for the consolidation of sensible painted surfaces in a perspectiveof a less intensive approach.