Sestertius - Trajan PORTVM TRAIANI S C

This sestertius commemorates the construction of Trajan's harbor at Portus, the artificial basin north of Ostia begun under Claudius and massively expanded by Trajan around 112 AD. The expanded hexagonal inner harbor, fed by a canal from the Tiber, was engineered specifically to bypass the chronic silting problems that had plagued the Claudian port. Rome's grain supply — the annona — depended on it, and Trajan's investment in the infrastructure was substantial enough to warrant a commemorative coinage. The harbor complex remained the principal import terminal for the city for the next three centuries.