St. Paul, oldest known image, 4th century CE.
The blog Quigley's Cabinet has picked up on a series of late June reports that the oldest known images of the apostles Andrew, John and Paul have been discovered and restored by archaeologists in a catacomb beneath an office building in Rome. Reports are here, here, here and here. The fresco images appear in an alcove housing a noblewoman's tomb.
Basilica of St Paul Outside the Walls, Rome. Photo by Berthold Werner.
Quigley's Cabinet: "Beneath an ugly office building ... lies a Roman time capsule. The catacombs of St. Tecla contain a tiny basilica where early Christians would celebrate Mass, corridors lined with niches for simple burials, and cubicles where the families of the wealthy were interred. One of these last is the frescoed tomb of a noblewoman now known as the 'Cubicle of the Apostles,' which has just been restored and represents some of the earliest evidence of devotion to the Apostles in early Christianity."
Above ground and not far from these crypts stands the Basilica of St. Paul Outside the Walls; according to Wiki, it's "one of four churches that are the great ancient major basilicas or papal basilicas of Rome." It was built over the burial site of the Apostle Paul himself. There is a view of the interior of the Basilica and Paul's tomb here.