Before the Christian religion adapted the basilican building format for religious purposes, a small secretive mystery religion used it first for their worship. The Porta Maggiore Basilica is a three aisled structure carved from the bedrock about 40 feet (12 meters) underneath the railroad yard of the Stazione Termini in Rome near the ancient Porta Maggiore. Railroad workers discovered it in 1917 when a passageway to the basilica caved in as they were building another rail line. The Statilius family, close to the Emperor Augustus may have built the structure sometime in the 1st century BCE. The scholarly consensus says that they built the Basilica for Neo-Pythagorean rites. Neo-Pythagoreanism was new at the time, an attempt to revive ancient Pythagorean mysticism combined with aspects of Platonism. The members of the sect were ascetics who renounced all worldly pleasures in the pursuit of a mystical union of the soul with its divine source. The rites that took place here were probably secret. The significance and the identity of a lot of the imagery in the basilica is forgotten.
Beautifully carved stucco images cover the interior of the Basilica. The artists added ground up mother-of-pearl to the plaster mixture to give the carved stucco a lustrous quality. Some of the carved figures can be identified such as Hercules and Orpheus, but most of the rest and their significance remain unknown.
Unlike the the third string house painters who made the later Christian catacomb art, these artists were first rate befitting an important family with ties to Augustus like the Statilius family known for their patronage of mystical and magical practices.
Since its discovery in 1917, preservation and restoration of the Basilica proceeded in fits and starts. A recent campaign added a concrete shell around the structure and ventilation to prevent radon gas build-up and to control humidity. It is now open to small groups of visitors who must make reservations in advance twice a month.