La Pedraja de Portillo was born between the waters of the Raso and a subsoil of gravels and sands

The shepherds would come down from the heights of Portillo with the sheep to graze them on the moorlands and pine woods of the Raso de Portillo. When the day’s work was finished, some would set up small camps so they did not have to return to the heights. Over time, those temporary settlements gave way to La Pedraja de Portillo.

The reason was not only the availability of grazing. The Raso was also an extensive wet area, a water landscape that covered around 1,900 hectares before being drained in the 19th century. The local ground, classified entirely as compact gravels and sands, forms part of that physical setting. Geology does not replace the history of the shepherds, but it allows the place that made it possible for them to stay to be viewed in a different way.

The Raso, far more than just grazing land

To imagine the origin of La Pedraja, it is necessary to set aside for a moment the current image of streets, houses and dry roads. According to the local history collected for the municipality, the Raso de Portillo was a wet area of enormous extent. There, the flocks that descended from Portillo met the open spaces of pasture and the pine woods that gave the landscape its name.

A wetland of 1,900 hectares was not just a simple transit point. It conditioned the livestock routes, the stops and the length of time people could remain in each place. The existence of water made it possible for shepherds not to rely only on returning every night to Portillo. It is likely that this combination of pasture and wetness encouraged the emergence of increasingly stable settlements, although historical documentation does not describe step by step how each camp was transformed into permanent housing.

The decisive change came when the Raso was drained during the 19th century. The operation altered the landscape that had attracted the first shepherds, but it did not erase the town’s relationship with water. The memory of the former wetland was incorporated into the life of the town through its wells, through its references to livestock and through the monuments that recall that dependence.

A subsoil of gravels and sands

The geotechnical information available for La Pedraja de Portillo identifies a single soil type: compact gravels and sands, which represent 100.00 % of the subsoil considered. No stratigraphic profile is provided with dated layers, nor is any specific geological age given for those materials. For that reason, it would not be rigorous to attribute them to a particular sea, lake or river.

What can be said, however, is that gravels and sands belong to the language of sediments that water can transport, deposit and reorganise. When they appear in a territory associated with a former wetland, they help to develop a coherent reading of the landscape: water was not an isolated element, but part of the configuration of the ground and of the resources that people used.

The hydrogeological sheet associated with the municipality adds an important caution. It describes formations that are generally extensive and, overall, of low permeability, although capable of hosting, at depth, aquifers of greater permeability and productivity, even of regional interest. That description does not show which aquifer fed each well, nor does it make it possible to reconstruct the exact mechanism of the former wetland. It does, however, make it reasonable to think that groundwater could have played a significant role in a place where local tradition preserves the memory of an artesian well.

Expansive clays that are subordinate are also identified, with a low to moderate risk of expansivity. They are not the dominant material of the subsoil and, on their own, do not explain the birth of the town, but they serve as a reminder that a granular ground can contain interbeds with a different behaviour when its moisture changes.

In any case, the key figure is the one that outlines the locality’s physical support: 100.00 % compact gravels and sands in the classification available.

The hamlet that was born from not having to return every night

The origin of La Pedraja de Portillo appears linked to a practical decision. The shepherds would come down from Portillo with their sheep, found a large grazing area in the Raso and stayed there long enough to form small camps. The distance between the place of origin and the area used for livestock grazing ceased to be a daily journey and began to turn into a form of residence.

Geology took part in that transformation in a specific, though not exclusive, way. The wet landscape provided the resource that made the stay viable, while the gravels and sands ground constitutes the material framework on which the settlement developed. It cannot be claimed that the soil type, by itself, founded the locality. Historical evidence points to the shepherds, the livestock, the moorlands, the pine woods and water as the elements that were combined to make it possible.

The difference is important. This is not a question of saying that a rock decided where to build, but of recognising that people did not choose their livestock routes in an indifferent space. The Raso had specific environmental conditions and La Pedraja emerged linked to them. The hamlet was the human response to a geography that was used repeatedly.

In the mid-19th century, by the time the Raso was already undergoing the transformation that would end its character as a wetland, La Pedraja de Portillo had 570 inhabitants. That figure shows that the pastoral settlement had stopped being an occasional grouping. The relationship with the territory had become a community.

Four wells for a life dependent on water

The old wetness of the Raso did not remain only in the description of the landscape. The town came to have four wells: two intended to serve as watering points for the livestock and another two to supply local residents. The division of uses shows the extent to which water organised everyday life. It was not an abstract resource or a secondary reserve; it had specific places, specific users and a different function depending on who came to it.

The artesian well occupies a special place in that memory. La Pedraja de Portillo has a monument dedicated to the artesian well of its forebears. The work does not, by itself, allow the depth, drilling date or the layers that contained the water to be known—data that do not appear in the documentation available. What it does confirm is that the memory of groundwater forms part of the municipality’s public identity.

There is significant continuity between the former Raso and those wells. First, the shepherds would take the flocks to a wet space with extensive grazing. Afterwards, drainage altered the landscape and made it necessary to preserve access to water through supply points. It is likely that the transformation of the wetland did not eliminate the need that had given rise to the first camps: to continue providing water to people and animals.

The monument to the artesian well turns that continuity into a visible object. Where the relationship with water was previously expressed through the shepherds’ routes and watering troughs, it is now expressed through a commemorative structure located in the urban space.

From the old tracks to the houses of the town

Human presence in the territory did not begin with medieval or modern shepherds. Local history mentions a post-Hallstatt-period ceramic site, the remains of a Roman road that ran towards Cauca—the current Coca—and some glass of Roman origin. These are different traces, separated by time and by their uses, but they indicate that the space was traversed and used before the present town was established.

Those remains should not be confused with evidence of direct continuity between the old settlement and La Pedraja de Portillo. The municipality’s own historical narrative places the birth of the locality mainly in the shepherds who came down from Portillo and in the camps formed along the Raso. The Roman road and Roman materials add a longer timescale: they show that the territory had value as a space for transit and occupation, whereas the wetland explains more clearly the specific history of the town’s origin.

With the establishment of a stable settlement came an architecture that today allows the community’s evolution to be followed. The Church of Our Lady of the Assumption (Nuestra Señora de la Asunción) was built between the 16th and 18th centuries. It has a hall-plan layout, with three naves of the same height, pillars and semi-circular arches; the main chapel is topped with a dome over pendentives decorated with Baroque plasterwork.

The wayside shrine of Christ (humilladero del Cristo) offers another view of the town. Its plan is square and it is built with masonry and brick, with the latter material reserved for the two semi-circular doors. In the 19th century, the cemetery was attached to it, later moved elsewhere. The documentation does not make it possible to affirm that the masonry came from the gravels of the local subsoil—a connection that would be easy to imagine but is not proven. What the building does show is how the landscape of shepherds and wells ended up being transformed into a core with religious spaces, dwellings and places of remembrance.

A land without earthquake as the main character

The local chronology consulted is not marked by a historically documented earthquake that conditioned the origin of La Pedraja de Portillo, the preservation of its buildings or the transformation of the Raso. The municipality’s history is structured around livestock grazing, the wetland, drainage and water supply, not around a seismic catastrophe.

The geotechnical information available also does not incorporate a local seismic series with maximum magnitude, number of events in the last thirty years, or the date of the last earthquake. Those values cannot be replaced by estimates. In this case, prudence matters as much as the data: nothing allows the seismicity to be presented as the force that brought the shepherds together or that changed the Raso.

The ground behaviour that is indeed indicated is different: the subordinate presence of clays with low to moderate expansivity. That warning belongs to ground management and not to the historical explanation of the settlement. The decisive footprint for understanding La Pedraja remains the relationship between a wet space, livestock routes and the availability of water.

When the Raso was a wetland, the shepherds found a reason to stay. When it was drained, the wells preserved part of that need. And on compact gravels and sands, the village transformed a livestock stop into a recognisable town, with a church, a wayside shrine and its own memory.

Today, the streets do not reproduce the landscape of 1,900 hectares of wetness that existed before the 19th century. But the monument to the artesian well and the history of the camps allow La Pedraja de Portillo to be read as the visible outcome of an old negotiation between water, the ground and those who depended on both.