A road begins with a surveyor
The work started long before the first stone was laid. Specialist surveyors, the gromatici, marked out the line with a groma, a surveying pole used to set out straight lines and right angles across country. That is where the famous straightness comes from. But a Roman road was straight only where the land allowed it. In hills, engineers preferred wide curves that kept the slope even, and where a river or a valley got in the way they built bridges and viaducts, or cut tunnels from both sides of a hill until the two teams met.
From the trench up
On a major road, workers excavated down to solid ground and then built upwards. The result was the agger, a raised embankment of compacted earth and successive courses of material: large foundation stones at the bottom, then broken stone and rubble, then sand and gravel, and, where it was available, lime mortar or concrete made with volcanic ash. On top came the surface. Near cities and on the most important routes, it was made of closely fitted paving stones; elsewhere, of firmly packed gravel.
The surface was cambered, that is, raised in the centre and sloping towards the edges, so rainwater ran off into ditches at the roadside. A road that sheds its water, on a bed that drains, stays firm far longer. Roman law set a minimum width of 8 Roman feet (about 2.5 metres) for a straight road and twice that on bends, though in practice widths and standards varied a great deal.
Four layers with Latin names?
Many books and websites describe every Roman road as four neat layers, often given Latin names such as statumen, rudus, nucleus and pavimentum, with their thicknesses. Is that how roads were built? Probably not in that form. The recipe comes from Vitruvius, the architect of Augustus’ time, and the chapter in question (book 7, chapter 1) is about floors and pavements inside buildings: a bed of stones big enough to fill a hand, a layer of rubble and lime beaten down to about three-quarters of a foot, a top layer of crushed pottery and lime, then the pavement. Roads are never mentioned. Real roads followed the same principle, a firm base under a hard surface, but their materials and thickness changed with the terrain, the traffic and what could be quarried nearby.
The Via Appia and the network
The first of the great roads was the Via Appia, begun in 312 BCE by the censor Appius Claudius Caecus. It ran 212 kilometres south-east from Rome to Capua and was later extended to Brundisium, modern Brindisi, on the Adriatic; with its later additions it is more than 800 kilometres long, and it was built and improved from 312 BCE until the fourth century CE. In 2024 it was added to the UNESCO World Heritage List as “Via Appia. Regina Viarum”, the queen of roads. By the beginning of the second century BCE, four other great roads already radiated from the city, and in the end the Romans built about 80,000 kilometres of hard-surfaced highway, from Britain to the Euphrates.
Roads came with a whole system of services. Mansiones offered rooms and supplies to government travellers; at the mutationes, official messengers changed horses. Inns, workshops, markets and whole settlements grew up at busy junctions, around forts and at river crossings.
Did all roads lead to Rome?
Symbolically, yes. In 20 BCE Augustus set up the Milliarium Aureum, the Golden Milestone, in the Roman Forum, and milestones in central Italy often gave the distance to Rome. In the provinces, though, the main city of each region was the hub of its own network, and the proverb itself is medieval: it was first recorded in 1175, by the theologian Alain de Lille.
Why they lasted
Good drainage and a deep, solid bed explain why the surface survived. The routes survived for a different reason. A line that crossed the land well, with an even slope and a reliable bridge, stayed useful long after Rome fell, so later travellers kept walking it and later states kept repairing it. Many Roman roads survive today, some as country tracks and some as streets inside the plan of a Roman town.
Where to see it
The best place to walk on a Roman road is the Via Appia Antica just south of Rome, inside the Parco archeologico dell’Appia Antica, where long stretches of the ancient paving survive between tombs and villas. In the Roman Forum you can walk the paving of the Via Sacra.
Sources
- Encyclopaedia Britannica, “Roman road system” (network, Via Appia, construction, width, stations, Golden Milestone, proverb).
- UNESCO World Heritage Centre, “Via Appia. Regina Viarum” (1708).
- Vitruvius, On Architecture 7.1.1-3 (trans. Gwilt, LacusCurtius).
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