In the old baptistery beneath the bell tower there lies a tombstone which, dating back to the 5th century, is a highly emblematic work, as it is one of the first examples of the presence of Christianity within the local context in the latter Roman period, confirming the survival of the settlement during the stage of the decline of Iluro in late antiquity, about which little is known.
It is a singular and unique piece of the highest order in the Catalan and peninsular archaeological landscape, because its head has a great Christogram in relief as an outstanding decorative, element with the Greek letters T (tau) and P (rho) overlapping each other, a variant of the monogram of Christ that served as a Paleo-Christian symbol, particularly widespread following the Edict of Milan issued by the Emperor Constantine.
It is a rectangular stone which once covered a tomb whose case was made with walls of stone and mortar. It has a single piece and was modelled on the site with a very fine layer of opus signinum (lime mortar and chippings of baked stone).
The tombstone was discovered during excavation work led by Marià Ribas, carried out in 1958 in front of the façade of the current-day church. While they were searching for traces of the necropolis of the former pagan temple and first Christian church, it appeared together with other funerary ensembles of lesser relevance.