Just outside Porta Maggiore in Rome, hidden seven meters below the current level of Via Prenestina, is the underground Basilica, a very interesting complex from the 1st century AD, accidentally uncovered in 1917.
It is the oldest example of a basilica structure found so far in Rome, a floor plan that, with three naves and an apse at the end of the central one, would become one of the canonical forms of Christian buildings. However, the Basilica of Porta Maggiore is a pagan temple most likely dedicated to Pythagorean cults, still shrouded in mystery today.
The complex consists of an access corridor, a quadrangular vestibule with a pavilion vault perforated by a skylight, and a main basilica-type hall divided into three naves covered with barrel vaults by six pillars. Noteworthy is the precious decoration of the miraculously preserved stuccoes depicting mythological scenes, paintings, and mosaics on the floors.
