In its upper reaches, the Navia River has many tributaries, such as the Ser, Queizán, Larxentes or Rao. Overlooking the area from the east are the Ancares mountains, as well as some parallel ranges arranged in a SE-NW direction, ranges which are divided by the aforementioned tributaries, in a type of morphology normally associated with Hercynian orogeny. To the south, the passes of Cebreiro, Piornal and Albela stand above the various headwaters. At Navia de Suarna itself, the valley is fairly open, but it narrows again as it proceeds north.
Approximately forty Roman gold mines have been identified in this area. Hard rock deposits are found along quartz reefs and Lower Ordovician slate belonging to the regional Los Cabos series. In the study area, few hard rock mines have been found in the northern part of the municipality. Most focused on the river terraces, which were of Quaternary alluvial origin.
The usual conglomerate found (boulders within a sandy or clay matrix) were systematically exploited in all the meanders, as well as in some of the tributaries. In most cases the alluvial conglomerate near the river were mined. But occasionally other deposits higher up were also tapped. In all, there were three levels: the higher one 150 m above the river, the middle one between 85 and 100 m, and the lower one, affecting the more recent terraces, were at most 40 m above the running water. Only when the alluvial deposits were thicker were more complex techniques used, such as trenches or contour strip mining. As Meduas, in Penamil, are a good example of this.
In some places mining fronts are clearly visible, despite continued farming activities, as well as the large accumulations of coarse tailings. These small-scale mines are present everywhere, revealing a systematic strategy carried out throughout all placer deposits of the upper Navia basin. Unfortunately, no evidence of the hydraulic infrastructure necessary has been identified yet.
Despite the small volume of earth removed in each one of the mines, a comparison between this area and neighboring ones reveals a very thorough approach by which all placer deposits were exploited. Even, at times, the riverbed itself was mined, as the examples of O Calexón or Pena Tallada reveal, enabling the panning of the river silt.