In ancient times, Roman roads were important arteries through which goods, people and ideas moved from one end of the vast Roman Empire to the other. Now new digital mapping reveals just how dense and extensive the Roman road network really was. Based on archaeological and historical sources as well as topographic maps and satellite images, the Itiner-e project team has mapped Roman roads in Europe, North Africa and Asia Minor with a total length of more than 299,170 kilometers. This increases the length of the identified and geographically recorded Roman roads by more than 100,000 kilometers. The new mapping is the most detailed and comprehensive digital road map of the Roman Empire. It provides valuable information for archaeological and historical research, but also highlights gaps.
At the height of its power and size, the Roman Empire had a population of more than 55 million. By the year 150, it spanned three continents – Europe, Africa and Asia – and reached from Spain and Morocco in the west to the Caspian Sea and Mesopotamia in the east. In order to transport goods and people – especially soldiers – from one place to another as quickly and efficiently as possible, a network of paved roads was built and continuously expanded. Unlike the mostly unpaved paths of other peoples, Roman roads had a foundation made of boulders, gravel and sand or clay on which the paving was laid. A curved surface and curbs ensured that rainwater did not accumulate but instead ran off to the sides. Similar to today’s road network, the roads varied in importance and length and the responsibilities also varied: wider, better-developed main roads between important centers were built and maintained by the central government in Rome, while regional and local road connections were under the control of the provinces or municipalities.
Search for Roman road connections
But despite its enormous importance in antiquity, the Roman road network has so far only been incompletely mapped. “There is a lot of information about Roman roads from archaeological excavations and mapping, and the milestones placed at regular intervals on the roads as well as historical sources describe the most important road connections between Roman settlements,” explain Pau de Soto from the Autonomous University of Barcelona and his colleagues. But collecting these many, very different sources and evaluating them as part of a comprehensive mapping is extremely difficult and time-consuming. “So far, there has been a lack of synthesis and digitalization that covers the entire Roman Empire,” say the researchers. So far, initial mapping of the Roman road network has shown a total length of around 100,000 to 180,000 kilometers.
To fill the gaps in knowledge about the Roman road network, de Soto and his colleagues launched the Itiner-e project. The aim was to digitally map the road network of the Roman Empire around the year 150 in high resolution and to make the available information on each road section available. To do this, they evaluated all the archaeological and historical data again. “The first step was to identify Roman roads based on previously published maps, archaeological surveys, milestones and regional mapping,” the team explains. The various data were compared with each other and brought into a uniform format. In the second step, the researchers used aerial photos and satellite images to specify the course of the road and the length of the paths based on traces and topography that are still visible today. In the third step, each identified and verified road section was individually digitized, georeferenced and saved as a layer in a geographic information system (GIS).
299,171 kilometers long and spread over four million square kilometers
The result is an interactive digital map that shows the Roman road network in unprecedented resolution and completeness. “Itiner-e includes any terrestrial route for which there is documented, estimated or assumed geographic information in the sources,” write de Soto and his colleagues. The map shows a total of 299,171 kilometers of roads covering an area of almost four million square kilometers. “This is almost twice the previously known length,” said the team. A particularly large number of previously unrecorded roads have been added on the Iberian Peninsula, in North Africa and in Greece. A good third of the Roman roads mapped in Itiner-e are trunk and main roads. Its total length is 103,478 kilometers. “This value is unlikely to change because these are the best documented and researched Roman roads,” the researchers write. However, the secondary roads, which make up around 65 percent of the mapped routes, are significantly less well researched. During the course of the research, large gaps in knowledge often emerged regarding their exact course or development over time. “Itiner-e makes these gaps in our current knowledge explicitly visible for the first time,” explain de Soto and his team. This makes it easier to conduct targeted research on this data in the future.
(Video: Itiner-e, Artas Media/ MINERVA)
The new map represents the most detailed and comprehensive digitization of the road network from the Roman imperial period available to date, as the researchers emphasize. “This resource can significantly advance our understanding of this period and reveal more about how mobility influenced relationships, administration, and even the spread of disease in the ancient world,” they write.
Source: Pau de Soto (Universitat Autònoma de Barcelona) et al., Scientific Data, doi: 10.1038/s41597-025-06140-z