What a harbour had to do
A good ancient harbour offered shelter from waves and wind, water deep enough for a laden ship, a safe place to haul out or moor, and space to store and move cargo. Most ports began as natural bays or river mouths and were improved over time with breakwaters, quays, warehouses and, for warships, covered sheds. Piraeus and Ostia show two quite different solutions: one a sheltered rocky peninsula with several basins, the other a river port that never had good natural protection.
Piraeus, the port of Athens
Piraeus lies a few kilometres south-west of Athens. The peninsula has three natural harbours. The largest, usually called Kantharos, served trade and the main fleet, while the smaller basins of Zea and Mounychia were used mainly for warships. Before the early fifth century BCE, the Athenians had mostly used the open beach at Phaleron, and Greek writers credit Themistocles with moving the city’s naval focus to Piraeus around the 490s and 480s BCE.
The harbours were then fortified and joined to the city by the Long Walls, built over the middle of the fifth century BCE. These walls meant Athens could be supplied by sea even while an enemy army occupied the countryside. That made the port part of the city’s strategy as well as its economy.
Excavation and later study have identified the remains of shipsheds, long covered slipways where triremes were kept out of the water to dry. Their size and number are useful evidence for how big the Athenian fleet could be, although the exact counts are still discussed by specialists. Many of the Athenian ships at Salamis came from this naval system. Silver from the Laurion silver mines paid for part of the fleet’s expansion.
Piraeus was also a commercial hub. A harbour district called the Emporion handled grain and other imports, and Athens relied heavily on imported grain. Writers also connect the town’s regular street plan with Hippodamus of Miletus, though how much he personally designed there is uncertain. The port was damaged badly during the Roman civil wars when Sulla’s forces attacked Athens in 86 BCE.
Ostia and the problem of Rome’s river mouth
Ostia sits near the mouth of the Tiber, roughly 25 to 30 kilometres from Rome by road. Roman tradition placed its beginnings early, and the earliest excavated fortified settlement is usually dated to around the fourth century BCE. The town gradually became Rome’s main river port, with warehouses, offices, apartment blocks, temples, baths and a theatre.
The Tiber carried silt, and the coast there has no natural bay. Large seagoing ships generally could not enter easily, so many anchored offshore and unloaded onto smaller boats, which then went upstream to Rome. This was slow and risky in bad weather, a serious problem for a city that needed imported grain.
Portus: Rome builds its own harbour
The emperor Claudius began a large artificial harbour just north of Ostia in the 40s CE. Two long moles enclosed a wide basin, and a lighthouse stood at the entrance. Later, Trajan added a hexagonal inner basin early in the second century CE, which gave ships a more sheltered mooring and made Portus the principal harbour. A canal and river links connected it with the Tiber and so with Rome. Engineers used Roman concrete to build breakwaters and quays, including in water.
After this, Ostia stayed important as a town, but Portus took over much of the heavy sea traffic. In late antiquity the area declined as political and economic conditions changed, and silting gradually took its toll.
Other harbour models
- Carthage had a distinctive circular military basin, known to Greeks and Romans as a kothon, according to ancient descriptions and excavation, though the details remain debated. The Punic cities were skilled harbour builders.
- At Alexandria, the Pharos lighthouse marked a coast with few landmarks, guiding ships toward the port.
- Caesarea Maritima in Judaea was an artificial harbour built under Herod in the late first century BCE, noted for its use of marine concrete.
What the comparison shows
Piraeus is a case of choosing and fortifying a good natural site to serve a naval state. Ostia and Portus show a state building around a hard geographic problem. In both, engineering, defence and economic planning were closely linked, and the ports’ fortunes followed those of the cities that depended on them.