Between the end of the 2^nd and the beginning of the 1^st c. BC the ekklesiasterion complex was completely covered and transformed into a square. The building known as the Oratory of Phalaris was erected on the west side of this square. The question of the function of this building has occupied many scholars who have forwarded numerous theories. It has been identified as either an heroon or as a tomb or, alternatively, as a shrine.

Today we know that Oratory of Phalaris was probably a small temple building, with a rectangular plan, on a high  podium decorated by mouldings  (m. 12.50 x 8.90), which was once preceded by a staircase, only the foundation blocks of which remain. The temple was a prostyle tetrastyle and the four Ionic columns of the façade supported a Doric frieze. The surface of the podium is 11 x 7.50 m., while the internal dimensions of the cella are 5.95 x 5.30 m. The entrance door to the cella, only the upper sections of which remain intact today, was of the Doric type. The walls are made of squared blocks of the local tufo and still bear traces of the stucco coating of the walls.

The cella was subjected to modifications carried out in the Norman, or an even later, period. It was transformed into a chapel, a fact which explains the name “oratory”. The dedicatory inscription of the temple is today preserved in the Archaeological Museum.