Three buildings dating from the late 2nd century B.C. overlooked the Forum square: the Basilica, the so-called “Antro delle Sorti” (sacred cave of the lots) and the Aula Absidata (Apsidal Hall). The Basilica, today a large uncovered courtyard, was the place where trials and any other legal matters were held. Originally it was divided into three aisles by two rows of columns, and perhaps enlightened by high windows set along the walls.
To the left of the Basilica there is the so-called “Antro delle Sorti”, an enlarged natural cave enriched by three niches with artificial stalactites. The entrance is monumentalised by a tuff blocks arch; the cave is paved in fine polychrome mosaic (2nd century B.C.) representing the seabed. Downwards to the right there was an altar possibly dedicated to Neptune.
Opposite to the Basilica, there is the so-called Apsidal Hall (Aula Absidata), nowadays embedded in the ex Archbishop’s Seminary. It is a large rectangular room equipped with counters decored with doric friezes and with an apse at the bottom. The apse was originally paved with the famous Nile Mosaic (2nd century B.C.), made locally by Egyptian craftsmen, now on display in the Archaeological Museum of Palestrina.
According to scholars’ theories, the “Antro delle Sorti” could have been a nympheum or a sanctuary dedicated to Isis or Serapis, whereas the Absidal Hall is interpreted as a library or a sanctuary dedicated to Isis.