A town drawn on an empty site
In 100 CE the emperor Trajan founded a military colony on the northern slopes of the Aurès mountains, in today’s Algeria: Colonia Marciana Traiana Thamugadi, now Timgad. Because it was built from nothing, its planners could draw exactly what they wanted. They drew a square enclosure, divided by a regular grid of streets, with two main streets crossing at right angles. Scholars call the main north-south street the cardo and the main east-west one the decumanus, and at Timgad both are still there to walk on.
A grid could also grow, and Timgad did: by the middle of the second century the town had spread beyond its original walls, with new temples, markets and baths in the new quarters.
The forum at the centre
Where the main streets met, or close to it, a Roman town placed its public square, the forum. Around it stood the buildings of public life. In Rome itself the Forum held temples, the Curia (the Senate house), basilicas for the law courts, and shops. At Nîmes, the temple now called the Maison Carrée stood in the forum of the colony of Nemausus, and it was dedicated to the heirs of Augustus, so even the religion of the square spoke of loyalty to Rome.
Water in, water out
A grid on a map is easy. Making a town work is harder, and Roman planners thought about what ran under the streets as much as the streets themselves. Roads brought people and goods to the gates. Aqueducts brought water to fountains and baths. And drains carried it away again: in Rome, the sewers started as a way to drain the marshy valley that became the Roman Forum. The geographer Strabo, writing under Augustus, singled out exactly these three things, roads, aqueducts and sewers, as what the Romans had planned best.
And Rome itself?
Rome was the opposite of Timgad. It grew over centuries on its hills and in the valleys between them, and no one ever laid a grid over it. What Rome did have were rules. Walls on a public street could be no more than a foot and a half thick, according to Vitruvius, so to house its crowds the city built upwards, storey upon storey. Augustus then forbade new buildings on public streets from rising as high as seventy feet, about 21 metres.
Many people lived in those tall apartment blocks, the insulae. The best place to see one today is Ostia, Rome’s port: the House of Diana, a second-century block of four storeys, had shops at street level and flats above, which became cheaper the higher you climbed, so the poorest tenants lived at the top.
So, a grid or not?
When Romans founded a town from scratch, a grid with two main axes and a central forum was the obvious choice, and Timgad shows it at its most perfect. When they took over an existing town, or built on difficult ground, they adapted. The constant was the package: a forum with its temple and basilica, paved streets, water brought from outside, drains to take it away, and rules about how high and how close people could build.
Where to see it
Timgad, about 480 kilometres south-east of Algiers, is a UNESCO World Heritage Site and the clearest Roman grid anywhere. Closer to home, Ostia Antica near Rome shows streets and apartment blocks on a large scale, and the Roman Forum shows a centre that grew without a plan.
Sources
- UNESCO World Heritage Centre, “Timgad” (194); “The Maison Carrée of Nîmes” (1569).
- Strabo, Geography 5.3.7-8 (trans. Jones, LacusCurtius).
- Vitruvius, On Architecture 2.8.17 (trans. Gwilt, LacusCurtius).
- Turismo Roma (Roma Capitale), “House of Diana, Insula of Jupiter and Ganymede and Insula of the Yellow Walls”.
- Livy 1.38.6 (drainage of the Forum valley).
