The interior of the basilica has a nave and two side aisles, concluding with a semicircular apse and two square apses. The aisles, with a higher central aisle, are divided by Doric columns, supporting an entablature. The presbytery, framed by a triumphal arch and delimited by Corinthian columns, is covered by a dome with eight segments resting on four tall corner columns. In the middle of the apse, in a niche, there is a frescoed monogrammed cross which, along with traces of faux marble decoration, are examples of the oldest painted decorations.
On top there is a Madonna with child and saint, a fragmentary fresco from the thirteenth century, and next to this a fifteenth century Crucifixion.
The origins of the church, initially dedicated to St. Concordio, probably date from sometime between the fourth and fifth centuries. After the Longobard restructuring in the eighth century, the church took the name of San Salvatore due to the image representing Jesus Christ, placed above the main altar. In the eleventh century the church regained the primitive name that lasted until the seventh century; again in the eighteenth century renovation work was carried out and the lantern on the dome was added.