The portus

a group of British archaeologists discovered a Roman theater in the south of Tibe river . First they found a navigation channel, with enclosures housing and gardens decorated with large columns. Archaeologists think that this port served as a resting point for Roman emperors. Called "Portus" this seaport, which is now removed from water by natural processes is being excavated by people from the University of Southampton, University cabridge and the British School of Rome. While there had been several digs in the area, no one had thought of the existence of this theater, only the archaeologist Rodolfo Lanciani in 1860 during the last major excavation on the site. Now, with the help of magnetic sensors, ground radar and metal probes, we could get a clear picture of the archaeological remains of the theater that has been dated to about the third century after Christ. Earle Greame notes that the area was used by a high official of the Roman state by luxurious materials used in construction and columns, has even come to think of that could be used by the Roman emperor himself. The grandeur of the theater also suggests that took place gladiatorial games, performances of naval or large animal fights. Another important finding within the site, is the head of a sculpture that may represent the hero Ulysses, who appeared at the time of Emperor Claudius, so we know that Portus was enlarged by Trajan in the second century AD. Archaeologists also believe that after the floods and the collapse of many Roman ships portus it became necessary to transport cereal flours create the Roman capital since that time Rome had grown and needed major ports such as Portus.

http://www.guardian.co.uk/science/2009/oct/01/archaeologists-find-rome-port-amphitheatre