A round temple on a high podium was in the centre of side II of the hexagon. It was built not later than the reign of Commodus, and dedicated to Liber Pater (Bacchus), as is shown by inscriptions. It was "excavated" by the Torlonia family. In 1864 an altar was found dedicated to Liber Pater Commodianus. A fragment of a curved architrave carried the name AVR RVTILIVS CAECILIA(nus). In the 15th century the statue of Bacchus was found, but thrown in the river Tiber by order of Cardinal Bessarion, who said it was sacrilegious. The temple was restored in the fourth century. It is in a prominent position, opposite the entrance to Trajan's harbour. The cult of Liber Pater seems to have been particularly important in Portus. It was associated with the cult of Bona Dea. Recent geophysical research (Keay 2005) could not confirm a round feature, but on this spot a square temple in a courtyard surrounded by a porticus (c 40 x 55 m.) seemed visible.
In 1794 the remains were found of a colossal statue of Trajan in military dress, in front of the Temple of Bacchus. It stood on a large base (4.46 x 4.46 m.) and was 5.57 m. high. It has disappeared.