There are no documents that ascertain the precise date of construction of the basilica. There is hypotheses, that the church was built between the end of the fourth century and the beginning of the fifth century, on the site where the remains of San Concordio, martyr, were buried. under Marcus Aurelius. After many restorations some elements of the early Christian era are visible.
See:
- Andre Grabar, L'Âge d'or de Justinien, de la mort de Théodose à l'Islam, Paris 1966