The spatial arrangement of the main stops considered by the previous authors reveals a significantly different distribution of sites in the territory. In our analysis, we have omitted some points that were considered very close to others, such as the case of Puente de Meyjaboy with Marzán or Iría Flavia with Padrón (Fig. 2).
If we compare these results with the initial MADO analysis, we can see how the optimal paths connecting the territory only coincide with specific segments of the proposed stops. This is due to two issues. The first is the slope of the terrain, which rises from barely 50 meters at Tui to 650 meters at Lugo. It is essential to consider that only 24% of the terrain is flat, with less than a 4º slope, 42% with a 4–12º slope, 21% with a 12–20º slope, and 14% of the territory with slopes greater than 20º. This general trend in the Galician territory, the heart of the area under study, greatly complicates mobility, with only a few natural paths. Additionally, this implies that the MADO analysis indirectly shows the three main routes to connect the three cities that we know for sure are their position in the territory: Bracara Augusta, Brigantium, and Luco Augusti, as mentioned earlier (Fig. 3).
The second consideration is that, clearly, the topography of the terrain has not been taken into account in the previous route calculations, as there are possibilities that are far from the main corridors. To address this, we conducted a second analysis of the routes with cost routes, connecting each potential stop with the next possibility (Fig. 4).
In this map, the optimal paths are nearly unique at the beginning from Tude to Aquis Celenis, with only one of the possible movements considered in one case. This implies that the territory is so challenging to traverse those options are limited. In the case of the West-East slope to Luco Augusti, the problem is more significant as there are more possibilities, along with an increased distance.
Figure 5. Detailed view from Tude to Burbida with LCP
The process of proposing an optimal route has relied on topographical considerations to define the corridors. In Fig. 5, a detailed view of the beginning of the road between Tude and Burbida is shown.
In this case, by visualising the terrain slopes and other features such as rivers, it becomes evident that mobility through the territory can only be achieved through the two corridors outlined as optimal. This implies that in this particular case study, the optimal paths closely resemble the surveyor's choice when selecting routes because there are no other viable options. In this regard, calculating not just the anisotropic distance, without considering the slope but the accumulated cost with topography, means that not all paths adhere to the miles provided by the itineraries.
In Table 2, the distance correlation between different stops can be observed after the route has been corrected according to topography.
Table 2
Distance correlation in meters between possible mansiones. In blue the proposed authors´ route.
Tude to Burbida | Burbida to Turoqua | Toroqua to Aquis Celenis | Aquis celenis to Tria | Tria to Assegonia | Assegonia to Brevis | Brevis to Marciae | Luco Augusti to Marciae |
16 miles | 16 miles | 14 miles | 12 miles | 23 miles | 12 miles | 20 miles | 13 miles |
23.696 | 23.696 | 20.734 | 17.772 | 34.063 | 17.772 | 29.620 | 19.253 |
Vigo | Sajamonde | Caldas de Reyes | Padrón | Sabugueira | Beigondo | Burgo de Negral | Burgo de Negral |
28.500 | 1.700 | 21.500 | 9.700 | 38.900 | 12.600 | 32.700 | 25.400 |
Vilar de Enfesta | Sta. Mª de Viso | Cuntis | La Estrada | Aixón | Vitiriz | S. Román de Retorta | S. Román de Retorta |
24.400 | 12.800 | 30.100 | 18.600 | 18.500 | 18.500 | 32.300 | 20.500 |
Mondariz | Tourón | | S. Miguel de Moreira | Quión | Melide | Marzán | Marzán |
32.300 | 22.400 | 23.100 | 35.800 | 23.300 | 32.900 | 24.700 |
Borbén | Pontevedra | | Oines | Castro a Golanda | Guntín | Guntín |
36.500 | 24.500 | 47.600 | 34.900 | 38.100 | 20.800 |
| Arzúa | |
52.700 |
Nuestra Sra. Del Viso |
39.900 |
Erbo |
45.900 |
Lalín |
42.900 |
The average distance value is greater than the theoretical mile of 1481 meters but close to that figure and relatively constant in all cases (1515–1550 meters):
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Burbida, Vilar de Enfesta, 24,400 meters (mile at 1525).
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Turoqua, Pontevedra, 24,500 meters (mile at 1531).
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Aquis Celenis, Caldas de Reyes, 21,500 meters (mile at 1535).
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Tria, La Estrada, 18,600 meters (mile at 1550).
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Assegonia, Quión, 35,800 meters (mile at 1556).
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Brevis, Vitiriz, 18,500 meters (mile at 1541).
Up to this point, all sites are consistent with the distances, with an average deviation of about 40 meters per mile. This discrepancy could be attributed to variations in the pattern or the calculation error with the optimal route, which is negligible. Therefore, we present this section without doubt.
The problem remains unresolved at the end of this stretch, as none of the mansiones align perfectly:
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Marciae, San Román de la Retorta, 32,300 meters (mile at 1615).
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Luco Augusti, Lugo, 20,500 meters (mile at 1576).
We believe that San Román is the most optimal, precisely because the calculations from Luco Augusti and Brevis are the closest. The itinerary would be arranged as follows, as depicted in Fig. 6.
Based on this information, we can propose that this is the best layout according to the topography, but we need to compare it with archaeological information. By selecting archaeological elements present in the territory, considering only those that provide information about a road (milestones in situ, excavated road remnants, bridges, or other elements from relevant locations such as hillforts, forts, or thermal complexes that could be potential stops on a road), we can assess the alignment. In the North-South stretch along the coast, there is no problem due to the abundant information provided by milestones. In the West-East stretch, we have summarised the main contributions in Fig. 7.
As can be observed, our optimal path is very close to key landmarks in the territory that provide information about the routes, such as the Taobada bridge, the Cuntis thermal baths (another possible mansio that would also be passed through), the toponym "A Estrada", and the Roman camp located there, the Boqueijón milestone, the Furelos Bridge, and the Calígula milestone in S. Román de la Retorta. There can only be uncertainty in three cases. The first, which is highly unlikely, is the Freixo bridge, isolated and outside any optimal route. The second is the path to the Friol milestone, which also deviates from the main routes. Only the possibility of passing through the Curbían thermal baths toward the milestone found in Entrambasaguas would make sense for the route to Guntín. In this case, this possibility is less likely since the Curbían thermal baths would not be a mansio in themselves. All these paths could well be other secondary networks that we are not aware of. Specifically, it might be worth considering whether the milestones of Friol, S. Román de la Retorta, and Entrambasaguas are not part of the Northeast - Southwest road that goes from A Coruña (Brigantium), to the South.
The results of the analysis clearly indicate that among all the scrutinized proposals, only those aligning with topographical distances hold merit. This effectively dismisses alternative possibilities that deviate significantly from the metrics provided by the examined itineraries. In light of these findings, a pertinent avenue for future exploration and inquiry arises: the extent to which there existed a genuine technical capability in Roman times to accurately measure these distances.
This prompts a crucial question that merits further investigation: Was there a realistic technical capacity in ancient Rome to precisely measure distances, especially considering the topographical intricacies of the terrain? The proposition emerges that the metrics found in historical itineraries might be regionally contingent, as empirical evidence suggests a misalignment with the actual geographical reality. Consequently, a reevaluation of the problem is suggested, leaning towards a Geographic Information System (GIS) study. Such a study could provide a more nuanced understanding by incorporating precise distances based on potential breaks in the orography, thereby offering a more accurate depiction of historical mobility patterns. This avenue for future research holds the potential to deepen our comprehension of the technological capabilities and spatial awareness of ancient civilizations.