The historic Pont del Diable , the Roman bridge connecting the towns of Martorell and Castellbisbal , is now showcasing the restoration of its iconic Roman arch on the Vallès side. This project brings to a close a long period of concern about the monument's condition, following the detection of structural damage more than a decade ago, which raised serious concerns about the bridge's fragility.
With an investment of around €412.000 , fully funded by the Barcelona Provincial Council , the work has consolidated the core of the arch, improved its stability, and ensured its long-term preservation. The administrations involved emphasize that special care has been taken to respect the bridge's status as a Cultural Asset of National Interest (BCIN) and its historical appearance—one of the few remaining structures of the ancient Roman road network along the lower reaches of the Llobregat River.
A two-thousand-year-old monument in a strategic location
Far from being a simple footbridge, the Pont del Diable (Devil's Bridge) stands at a key location where the ancient Via Augusta crossed the Llobregat River , forming a communications hub that was already strategic two thousand years ago and which today remains surrounded by roads and railways. Built between 16-13 and 8 BC , the bridge bears traces of the Roman legions IV Macedonica, VI Victrix, and X Gemina , which participated in the major public works projects of the Augustan period.
Its ashlars and stone blocks, from the same quarries that supplied Roman engineers, have withstood centuries of floods, wars, and reconstructions. However, continuous exposure to the elements and the aging of the materials had left the Roman concrete core exposed , initiating a process of degradation through sand formation and loss of volume that threatened the arch's stability.
The president of the Barcelona Provincial Council, Lluïsa Moret , emphasized during the inauguration ceremony that it is “admirable that the bridge has become a true element of local identity and cohesion, a popular and iconic image, and that it continues, two thousand years and several reconstructions later, to be situated at a strategic crossroads of paths, roads, and railways.” She added that the preservation of the Roman arch reinforces the symbolic value of this crossing between regions.
The Pont del Diable (Devil's Bridge) is today one of the few Roman civil works that still directly bear witness to the network of imperial roads in the lower Llobregat region. Its silhouette, easily recognizable, acts as both a boundary and a link between the Baix Llobregat and the Vallès Occidental , becoming a territorial marker shared by Martorell and Castellbisbal.
Having surpassed the threshold of two thousand years of history , the bridge has survived periods of neglect, sporadic repairs, and extreme weather events. The recently completed restoration is seen as a turning point in halting the deterioration that had accelerated following the rockfalls detected more than ten years ago.
A decade of studies to tackle a “great technical challenge”
Visible problems began when the first stones from the arch's internal fill were observed to be falling, forcing the authorities to take action. Starting in 2013, the Local Architectural Heritage Service (SPAL) of the Provincial Council initiated a comprehensive diagnostic phase that lasted for years and which the technical project itself describes as a "major challenge" due to the monument's complexity.
In this preliminary stage, no improvisation was necessary: laser scanning was used to obtain precise three-dimensional models of the arch, along with structural stability studies that identified the most fragile areas. Simultaneously, ground-penetrating radar surveys were conducted to detect cavities and discontinuities within the Roman concrete core, invisible from the outside.
The diagnosis was completed with inspections using infrared thermography , a technique that allows for the location of moisture, leaks, and internal voids based on temperature differences in materials. Thanks to this set of high-precision tests, the technicians were able to design a intervention tailored to the actual pathologies of the arch, without resorting to aggressive or disproportionate solutions.
The designation as a Cultural Asset of National Interest also required extreme caution. Any intervention had to guarantee both structural safety and the preservation of the monument's historical appearance. Therefore, the study phase analyzed not only the condition of the original Roman material, but also how previous interventions and the bridge's immediate surroundings had affected it.
This preliminary work, less visible but fundamental, allowed us to begin construction with a very detailed understanding of the structure: where the cracks were concentrated, what areas were empty inside, how the Roman mortar behaved in the face of humidity, and which points were most exposed to rainwater leaks.
Eleven months of work to fix the heart of the arch
The physical execution of the restoration began on February 3, 2025 , and lasted for eleven months . The core of the project focused on securing the stones of the Roman fill that were threatening to detach, as well as controlling the sanding process that was affecting the ancient mortar.
To achieve this, the technical team designed a specific lime mortar , formulated expressly to be compatible with the original materials from two millennia ago. This mortar was injected into the interior of the arch following a grid pattern of perforations , which allowed the internal voids to be filled and the core of the structure to be consolidated without altering its exterior geometry.
In areas where the fractures were more complex, carbon fiber bars were used as a crack-stitching system. This solution, common in interventions on historical heritage, offers high resistance with minimal visual impact, as it is completely integrated within the material.
The work included the meticulous reintegration of stone pieces inside the arch and at the bases of the columns. The specialist firm Cyrespa Arquitectónico SL recovered blocks of bioclastic calcarenite and red stone (Buntsandstein) from the same historic quarries used in Roman times, to ensure the closest possible match with the original elements.
Joan Closa , manager of the Barcelona Provincial Council's Department of Equipment, Urban Infrastructure, and Architectural Heritage, explained that the arch "was badly damaged and in very poor condition." Following the restoration, he assured, the structure is stable and many of the problems associated with water infiltration have been resolved by filling an interior that "was half empty" and removing soot and dirt.
Controlling the water and camouflaging the intervention
One of the most serious problems detected in the arch stemmed from rainwater seepage , which seeped through the top and accelerated the internal degradation of the Roman concrete. To stop this deterioration at its source, a copper sheet roof has been installed in the center of the arch , designed with four slopes and a gargoyle that channels the water away.
This metal sheet will not be visibly exposed. Over time, the copper will develop a natural patina of oxidation that will help camouflage its presence, making it virtually imperceptible to the naked eye. The aim is for the water-repellent protection to fulfill its function without altering the historical character of the monument.
From an aesthetic point of view, the guiding principle has been that the restoration should be as inconspicuous as possible. Although the restored areas are currently lighter in color compared to the original stone, Closa emphasized that the effects of rain and the passage of time will gradually even out the tone until the difference is much less pronounced.
To soften the contrast between the new and the old, a transparent glaze with mineral pigments , based on iron oxides, has been applied . This technique openly acknowledges which parts have been restored, but at the same time helps to unify the overall color scheme, preserving the "historical memory" of the textures and the patina accumulated over centuries.
In addition to the arch itself, the project has encompassed the immediate surroundings of the access point on the Castellbisbal side. Some gaps in the Roman-era stone slabs have been restored, paving has been repaired and consolidated, and the protective treatments and finishes of the railings have been renewed, improving both safety and the overall appearance for visitors and residents.
The project also included a general cleaning of the monument's surface, removing soot deposits, environmental dirt, and remnants of previous interventions that partially obscured the original Roman structure. This cleaning was carried out using low-impact techniques, selected to avoid damaging the historical material.
A symbol shared between Martorell and Castellbisbal
The official reopening of the restored arch was celebrated with an institutional ceremony attended by Lluïsa Moret, the mayor of Castellbisbal, Maria Dolors Conde , and the first deputy mayor of Martorell, Lluís Amat . The joint presence of representatives from both municipalities underscored the shared nature of the monument, which serves as a point of connection between the two banks of the Llobregat River.
During the inauguration, a commemorative plaque marking the restoration was unveiled , officially commemorating the long-planned project. According to those in charge, the work had to be carried out carefully to ensure a result that respected the bridge's heritage value. The Barcelona Provincial Council emphasized that the local architectural heritage department assumed full responsibility for the technical direction and execution of the project.
Moret used his speech to emphasize the role of the Pont del Diable (Devil's Bridge) as a symbol of territorial cohesion . In his opinion, the bridge not only physically connects Martorell and Castellbisbal, but has also become a consolidated element of shared identity, very present in the popular imagination of the area and in the way residents recognize themselves in their surroundings.
Local institutions appreciate that, thanks to the renovation, the long-term survival of a key piece of Barcelona province's heritage is guaranteed. Beyond tourism or its picture-postcard appeal, the bridge maintains an educational function as a living example of Roman engineering and the historical continuity of communication routes along this stretch of the Llobregat River.
The project budget, estimated at approximately €412.369,51 and fully funded by the Provincial Council, is considered appropriate given the level of expertise required for this type of intervention. The combination of advanced preliminary studies, compatible materials, and discreet consolidation techniques has aimed to strike a balance between conservation, safety, and historical accuracy.
With the scaffolding now removed and the access area renovated, the Roman arch of Pont del Diable once again stands proudly above the Martorell gorge, displaying a more refined appearance while retaining its centuries-old character. The restoration culminates a long and technically complex process that has addressed the monument's main structural issues, reinforced its stability against the ravages of time, and reaffirmed its role as a key heritage site of the Roman road network in Catalonia and as a shared emblem of Martorell and Castellbisbal.
