Roman Empire's road network was 59% larger than previously thought

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Rome wasn’t built in a day . All roads lead to Rome . A recent study now links those two well-worn proverbs by suggesting that the footprint of Roman road infrastructure was 59% larger than previously thought. The revelation isn’t just quantitative — a network with a finer mesh might change what we think life was like across Rome’s vast domain.

From Hadrian’s Wall to the Persian Gulf

The findings come from the research team behind Itiner-e, a project that published a digital atlas of the Empire in Nature’s Scientific Data in late 2025. They mapped about 186,000 miles (just under 300,000 km) of roads across Rome at its greatest extent. This was in the 2nd century AD, when the Empire sprawled from Hadrian’s Wall in northern England to the western shores of the Persian Gulf. The previous reference catalog, the Digital Atlas of Roman and Medieval Civilizations (DARMC, now known as Mapping Past Societies), tallied around 117,100 miles (188,500 km) — meaning the new figure is 59% longer than the earlier total.

Roman roads transported more than people and goods, they also moved ideas and religions to faraway places, as shown by this altar to the Persian god Mithras, discovered in 2010 in Scotland, at the very northern edge of Rome’s road network. ( Credit : National Museums Scotland)

To be clear, the researchers have not discovered that Rome had a secret “lost” highway system. They didn’t discover a massive imperial ring road or dig up a legionary engineering project concealed for two millennia. The explanation is less Indiana Jones, more Beancounter Bob.

Earlier compilations of the Roman road network tended to privilege great, well-documented routes like the Via Appia (Rome to Brindisi) or the Via Egnatia (from Albania’s coast to Byzantium). The connective tissue between those major roads — the first- and last-mile bits that actually got produce to market, villagers to town, soldiers to frontiers, and tax collectors to your door — received less attention.

What the Itiner-e researchers did was create, from a wide and scattered body of evidence, a much fuller and more precise record of roads that definitely existed, and also ones that researchers suspect existed, with varying degrees of confidence.

Itiner-e’s final result makes the imbalance plain. Of its roughly 186,000 miles of roads, only about 34.6% are classified as main arteries. The remaining two-thirds are secondary routes or smaller. Roman roads were much like ours: a mixture of grand highways, regional roads, and rural lanes. While the major thoroughfares get all the press, the smaller ones probably played an important part in everyday work.

Cold War spy satellite photos, repurposed

As an international project with contributors from the universities of Barcelona and Aarhus, among others, Itiner-e built its Roman road atlas (the expanded version) in three painstaking phases.

First, they drew on literary sources, inscriptions, gazetteers, excavation reports, and earlier atlases to identify where the roads should be. Then, they used satellite imagery, aerial photography, and topographic maps to determine where those roads did plausibly run. And finally, they digitized the whole thing, segment by segment, into a geographic information system.

A sample of DARMC road mapping in southern Britannia and northern Gaul (now the southern UK and northern France, plus the Low Countries, respectively). Note how the course of Roman roads still corresponds to present-day centers of night-time luminescence (e.g. the roads converging on London). The more extensive road network formulated by Itiner-e may not only teach us more about how ancient Rome worked, but also how its infrastructure has influenced the societies that came after the Empire and continues to affect the present. ( Credit : Mapping Past Societies/Harvard University)

Among the images the researchers used were Cold War-era spy satellite photographs — now used to spot infrastructure much older than the type that intelligence agencies were looking for in the 20th century. Even centuries after their disappearance at, well, street level, Roman roads can still be identified from above as subtle marks in fields, slight differences in vegetation, and subtle traces in the terrain.

The resulting atlas is not, however, a definitive catalog. Its most salient feature may be that it evaluates how confirmed or contested each mapped route actually is. In fact, only 2.7% of the total length is classed as certain , meaning there is a physical road surface left from Roman days. Nearly 90% is conjectured : inferred from a web of literary references, terrain logic, and pattern-matching. The remaining 7.4% is outright hypothetical .

The latter two categories are not an admission of failure. They visualize a problem that most Roman road maps all too easily conceal: a clean line on paper (or screen) can look much more definitive than the evidence behind it. Or to be blunt: They’re often scholarly best guesses dressed up as solid roads.

To let the evidence, current and future, have the last word, Itiner-e attached source information and confidence assessments to each road segment. Later researchers can then continue the fight over which highways and byways need to be refined, challenged, or scrapped altogether from the map.

Itiner-e wears this uncertainty as a badge, not a blemish. The idea is that in historical research, a frank and open assessment of uncertainty will lead to a higher form of precision. That key principle of the scientific method is ignored all too often, and not just in Roman studies.

The oldest evidence of the Roman road network

This modern, layered, conditional map is the digital descendant of the Tabula Peutingeriana . Itiner-e’s strange and magnificent ancestor is the oldest cartographic evidence we have of the Roman road network. But not quite as old as Rome itself: the Tabula is a copy on medieval parchment of a map tradition that harkens back to the time of Augustus. That copy, dating from the 12th century and now at Austria’s National Library in Vienna, thus only provides indirect evidence of how the Romans themselves mapped their roads.

Two examples of how Itiner-e has increased our understanding of the extent of the Roman road network: adding a lot of mileage in some areas, such as northern France (top), and considerably less in others, such as southern Turkey (bottom). ( Credit : Itiner-e: A high-resolution dataset of roads of the Roman Empire, in Nature)

Measuring 6.75 meters by 34 centimeters — the dimensions of an unwieldy scarf — the Tabula is not a map in the classical sense (pun intended) but rather a route diagram. It compresses the north-south dimension, stretches coastlines, and rearranges geography to make routes and distances legible.

The Tabula depicts more than 550 cities and 3,500 other place names, along with the way stations and distances that separate them. It covers the Empire itself, but stretches all the way to India, showing how the grasp of Rome’s geographic imagination exceeded its actual reach. One segment is missing, so Britain is not fully represented on the Tabula , which otherwise is a remarkably intact witness of Rome’s practical attitude towards mapcraft: no Here be dragons , or other mythical or religious infusions that distorted later maps.

With its focus on connectivity rather than geographical accuracy, the Tabula weirdly prefigures the schematic and now-iconic map of the London Underground, designed by Harry Beck some 1,900 years later.

Itiner-e draws on the Tabula and many other sources, but the contrast is revealing. Where the Tabula is visually eccentric, Itiner-e is digitally exacting. Both, however, show that mapping a road network is not just a matter of sticking to the main roads. It’s a matter of deciding what counts as a road, and that in the context of what the map wants us to understand.

Roman roads may have been a military construct to start with; they eventually did much more than just move legions across the Empire. They were vital for Rome’s trade, commerce, and administration. They connected markets and ports, farms and urban settlements. And they facilitated not just the flow of people and goods across one of the largest Empires in history, but also of ideas and religions.

Rome’s version of the Pony Express

A second-century altar to the Persian god Mithras, discovered near Edinburgh in 2010, would never have made it to Scotland if not for the Roman roads, which extended north of even Hadrian’s Wall. Around that time, Christianity was already seeping into Gaul via the same road network.

The Empire even had its own version of the Pony Express. The cursus publicus kept a chain of stations every 12 to 23 miles, each stocked with fresh horses to move official communications at speeds that were extraordinary by premodern standards. Switching mounts as they went, a courier could typically cover around 50 Roman miles (about 46 miles, or 74 kilometers) a day, an extraordinary speed by premodern standards. In an emergency, he could go much farther. According to the sixth-century historian Procopius, couriers could cover in a single day a distance that would ordinarily take ten. Call it the Roman version of broadband — but with hooves, and a taste for carrots.

Detail of the Tabula Peutingeriana, with at its center a symbolic representation of Rome, and the medieval idea of what a Roman emperor might have looked like. ( Credit : Konrad Miller/Bibliotheca Augustana – public domain)

The denser road network revealed by Itiner-e gives historians a different and more detailed model to work out how that connectivity operated in practice. Researchers can make more precise judgments about how fast news and soldiers travelled, how supply chains and regional trade networks fit together, and how people and ideas — and also plagues and diseases — migrated across the Empire.

If smaller settlements off the main highways were plugged into the main network via local routes, their relationship with the wider world was likely more immediate than previously assumed. In other words, Rome’s Empire, and its economy, may well have had more coherence and churn than we thought.

It’s tempting to see the new map as another example of Rome’s superlativeness, more proof the Ancients were even better at everything than we thought. But that is not quite the point. The famous routes still deserve their fame. But it is now clearer than before that the Empire was not held together by grand avenues alone; it also depended on provincial lanes, market roads, harbor routes, and other lesser tracks connecting unsung places.

Yes, all major roads led to Rome. But the Eternal City owed much of its vitality and longevity to the capillary network of streets and lanes that linked amphora traders, shepherds, and itinerant fortune tellers not just to Rome, but to just about every small town and settlement in the Empire.

Strange Maps #1304

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This article Mapped: Every known (and suspected) road in the Roman Empire is featured on Big Think .