Claudius undertook the construction, which Caesar had planned, of an enclosed harbour two miles north of Ostia, linked to the Tiber by a canal: to remedy the very difficult conditions of trans‐shipment at Ostia; to provide Rome with a worthy gateway for seaborne visitors; and to help mitigate floods at Rome by improving the flow of the Tiber. A deep basin was excavated and protected from the sea by two moles, with a lighthouse rivalling that of Alexandria.
The new harbour was not safe, as its wide-open expanse was prone to squalls; disaster struck in 62. Trajan undertook the construction of an inner basin at Portus, hexagonal in plan, covering 32 ha. (79 acres), which rendered the harbour usable (despite some problem with silting) throughout antiquity.
Subjects: Classical Studies.