The Trajanic harbour

The Emperor Trajan substantially enlarged the Claudian harbour at Portus. His aim was probably to provide the necessary storage and transhipment facilities for the supply of grain from Alexandria to Rome, which had hitherto gone to Puteoli (Pozzuoli) on the Bay of Naples. His scheme, known to archaeologists as the Port of Trajan (Porto di Traiano), involved the excavation of an enormous hexagonal pool inland, just behind the still-functioning harbour begun by Claudius, and connected to it by a short canal.

The centrepiece of this new enterprise was a large hexagonal basin which was built a short distance to the south-east of the main basin of the Claudian port. It was designed as an inner harbour, possibly as a large-scale replacement for the earlier Darsena, able to accommodate a larger number of ships. It also had more extensive storage facilities than before, with the construction of large warehouses along at least five of its six sides. Furthermore, it also incorporated the Darsena and surrounding areas, and the construction of a new canal complex that connected the earlier "Fossa Traiana", the hexagon and the earlier river port. Access to the growing settlement on the Isola Sacra on the south bank of the "Fossa Traiana" was provided by a road that was carried across the "Fossa Traiana" by the Pons Matidia and continued southwards to Ostia as the Via Flavia. Once completed, the integrated complex of the Port of Claudius and the Port of Trajan functioned as a unified whole.