The Roman Empire's road network is one of the greatest engineering feats of antiquity. A new digital catalog has estimated the total length of these roads at nearly 300.000 kilometers, according to the journal Scientific Data. However, the most striking aspect is not the figure itself, but how little we know about it: only 2,7% of its route is known with certainty.
This project, dubbed Itiner-e, has mapped 103.478 kilometers of major routes, but its authors warn that most of the paths remain a mystery. The infrastructure that once connected the entire Mediterranean with Northern Europe has left hardly any identifiable traces, and experts have been debating why for years.
A catalog with surprising figures
The Itiner-e catalogue, published in November 2025, is the most comprehensive to date. It compiles data from thousands of archaeological sites and historical documents to reconstruct the road network of the Roman Empire. Despite its ambition, researchers acknowledge the enormous uncertainty: of the estimated 300.000 kilometers, we can only pinpoint the location of about 8.000 with certainty.
This lack of knowledge is not accidental. Most Roman roads were reused, destroyed, or simply abandoned after the fall of the Empire. In many cases, the routes were lost beneath modern roads or farmland, and only small, isolated sections remain.
Rome's fall and the technical slowdown
Engineer Isaac Moreno Gallo, an expert in Roman public works, has spent years defending a controversial thesis: the fall of the Empire not only brought about a political change, but also a brutal technological setback . In his interviews, he quotes a phrase attributed to astronomer Carl Sagan: "If the Roman Empire hadn't fallen, man would have reached the moon by the year 1000."
Moreno Gallo explains that the political fragmentation following the collapse left the kingdoms without the capacity to maintain infrastructure. An aqueduct without maintenance deteriorates in just a few years, and a road disappears even faster . The result was a period of technical stagnation that lasted for more than a thousand years, until the 19th century when the level of knowledge was recovered.
The recovery in the 19th century
In Spain, the road network was not planned on a comparable scale again until the Highways Act of 1857. In just eight years, the kilometers built increased from 11.277 to 17.503 , according to historical data. This resurgence coincided with the creation of the School of Civil Engineers, which trained the technicians capable of undertaking such a project.
Moreno Gallo, who has reconstructed instruments such as the chorobate and the dioptra, insists that Roman engineering was far more advanced than commonly believed . His field research demonstrates that the roads were designed for carts, with gentle slopes and durable surfaces, something not seen again until the industrial era.
Ultimately, the legacy of Roman roads remains largely a mystery. The Itiner-e catalogue has taken the first step in mapping a network that shaped the development of Europe , but much remains to be discovered. Meanwhile, Moreno Gallo's thesis reminds us that progress is not linear, and that sometimes, as he says, "the more you discover, the further away the end seems."