Italy's coastline possesses few natural harbours and in early imperial times several artificial ones were constructed to cater for the increasing volume of seaborne trade.
The emperor Claudius (AD 41-54) ordered an artificial harbour to be built near Ostia at the mouth of the river Tiber to ensure Rome's grain supply. These works consisted of two curved harbour moles with an artificial island in between. A lighthouse, modelled on the Hellenistic Pharos at Alexandria, was erected at the harbour's entrance.
Despite these improvements the Roman historian Tacitus records that many ships continued to be lost in rough seas. Under Trajan in AD 112 a sheltered hexagonal harbour basin was built, which was connected to the Tiber by means of a canal.
The use of a hydraulic cement which set under water made such harbour works durable, but at Ostia and elsewhere regular dredging was needed to prevent them from silting up.
