Neither all the roads went to Rome nor were they so straight

Barcelona"All roads lead to Rome" is an expression that has been used to speak about geography, religion, or as a popular saying to mean that there are different ways that lead to the same result. However, science has just debunked this myth. Research led by the archaeology team at the Autonomous University of Barcelona (UAB) has shown that the Roman Empire's mobility network did not have the capital as the navel of the world.

The work, which has been published in the journal Nature Communications, is the result of six years of research. The team of archaeologists has been collecting, analyzing, and adding up all the research that has been done from the end of the 19th century to the present day with the goal of building Itiner-e, the most detailed and complete digital map, according to the UAB, of the Roman road network created to date. Itiner-e covers five million square kilometers across the entire Mediterranean arc, North Africa, the Middle East, and Europe. "We have searched region by region and we have unified the data because different criteria and scales were used in each place," explains Pau de Soto, archaeologist and Serra Húnter associate professor at the UAB. "Until now, most studies only took into account around 50% of the known roads and the conclusions that were obtained were much simpler. We have managed to collect and digitize nearly 90% of the roads, and the result is a much more complex and realistic map of what true mobility was in Antiquity," says De Soto.

The spatial analysis of Itiner-e demonstrates that the Roman Empire was structured through regional networks articulated around provincial capitals, seaports, and river corridors. Rome is in the center-west of the Italian peninsula, and this geographical location also complicated everything. "If we look for the point where the routes of all continents actually meet, that is Byzantium," the researcher argues. The future Constantinople and current Istanbul, therefore, was the true geographical articulation node of Antiquity: "Byzantium is located at the exact point where the routes from Europe to Asia connect, and where you had to pass through if you were coming from northeast Africa or East Asia. Thinking about the geography of the entire empire, Byzantium was a much more strategic point, which explains why it became the capital of the Eastern Empire and ended up lasting many more centuries," he adds.

Another of the myths that research debunks is that of Roman roads as perfectly straight lines that ignored topography. "We all have in mind the image of the Appian Way, with straight and paved axes, and we tended to idealize the entire network based on these examples," indicates the archaeologist from the UAB. However, the analysis of more than 300,000 kilometers of roads reveals that the Romans were very pragmatic and that politics always had an important weight. "Where it interested them most, such as in the Alps to connect Italy with the rest of Europe, they dedicated huge resources to make straighter roads with better slopes. In contrast, in other mountain ranges or areas of less strategic interest, they adapted more to the terrain," asserts De Soto.

Designing this network without current technology, and without satellites that can provide a global view from the air, required a huge amount of work. They did it all on foot, walking, exploring, and also taking advantage of the knowledge and paths that had already been traced by the societies they conquered. Roman engineers used precise topographic tools to keep slopes below 16%, an important limit for the transport of goods. "In Roman times, the great technical problem was not climbing mountains, but descending them and how to brake carriages," explains the researcher.

The imprint on the current urban map

The survival of this network from two millennia ago is still visible today, although with great differences depending on the region. "One of the main keys to the continuity of the routes is the maintenance of the cities: many of the cities where we live today have a Roman origin and it is very logical that the connecting corridors have been maintained," says De Soto.

However, the industrial revolution changed the map quite a bit. "Regions like northern Germany or the Netherlands, which in Roman times were border or secondary zones, have multiplied their road network enormously with industrialization to become the nerve center of Europe. In the same way, very centralist current capitals like Madrid or Paris did not exist or had no weight in the design of the Roman imperial network," details the archaeologist.

The development of Itiner-e has required a great deal of documentary research. "We have spent more than five years collecting and digitizing data, without using artificial intelligence, and this last year doing complex calculations," details the UAB researcher. The objective of the tool created by the UAB team is not only cartographic, but also seeks to answer many other questions. "Creating this resource was fundamental because transport is linked to everything: to the economy, to the circulation of ideas, to the expansion of religions like Christianity and to the spread of diseases," warns De Soto. "We know where the great epidemics of Antiquity originated, but until now we lacked the map of the network through which they expanded. Now that we have this tool, we can begin to answer all these historical questions," adds Pau de Soto, who, with the UAB team, will continue researching to be able to establish a chronology of terrestrial networks and add maritime and river networks.