Just outside Porta Maggiore in Rome, hidden seven meters below the current level of Via Prenestina, lies the Underground Basilica, a very interesting complex from the 1st century AD, accidentally brought to light in 1917.
It is the oldest example of a basilica structure discovered so far in Rome, a floor plan that, with three naves and an apse at the end of the central one, will become one of the canonical forms of Christian buildings. The Basilica of Porta Maggiore is, however, 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 pierced by a skylight, and a main basilica-type hall divided by six pillars into three naves covered with barrel vaults. The precious decoration of the stuccoes, miraculously preserved, depicting mythological scenes, paintings, and mosaics on the floors stands out.
