Archaeological remains at Ponte Milvio could be one of Rome's earliest churches.

Archaeologists are baffled over an important discovery of the remains of ancient Roman buildings, dating from the first to fourth century AD, along the banks of the river Tiber at Ponte Milvio in north Rome.
Experts believe the lower part of the remains, dating from between the first and second centuries, belonged to a warehouse or a commercial enterprise of some kind.
Archaeologists are uncertain however about the purpose of the building on the higher level whose floors and walls feature precious coloured marbles from northern Africa. This section dates from the third to fourth centuries and could have been part of a Roman villa.

However given its close proximity to a small cemetery, whose skeletal remains are still intact, experts have not ruled out that the building could be one of the city's earliest churches. 
The remains were discovered by chance during the routine laying of electric cables by technicians from ACEA, the municipal authority in charge of supplying Rome with electricity and water.
Excavations began last autumn at the site, located under a bicycle track close to the Milvian Bridge, scene of the historic battle between rival Roman emperors Constantine I and Maxentius in 312.
Constantine won the battle, leading eventually to his ascension as sole ruler of the Roman empire and the subsequent adoption of Christianity as the empire’s official religion.