Last modified on Sun 9 May 2021 12.15 EDT
By the 1st century AD, Rome had a population of about a million people, far more than could be fed from local sources, so was dependent on supplies from across its Mediterranean-wide empire. However, its access to the sea was limited as the Tiber mouth at Ostia could accommodate only small ships. Cargoes were thus shipped to the Bay of Naples and taken overland or by smaller boats to Rome.
A hungry population threatened political instability, but it was not until the AD 40s that the Emperor Claudius initiated the construction of Portus on the coast just north of Ostia, with huge concrete moles enclosing a 69-hectare (170-acre) anchorage with a lighthouse at its mouth.