The former mine of Val d’Arca is located in the western part of the municipality of Sabugal, district of Guarda. It is situated near the village of Quarta-Feira in a steep valley close to the sierra of São Cornélio.

This mine, which began operating in the early twentieth century (1917-1923), was first mined for radium through two galleries on a hillside, and was reformulated during a second phase by the Companhia Portuguesa de Rádio (CPR). At the time, uranium was seen as a crude byproduct of little interest. This attitude only changed in the 1940s, and by the time the mine closed in 1961, more than 32,000 tons of this ore had been extracted. The mine was operated using 3 floors and 6 inner shafts, the ore being extracted through the galleries mentioned above. The master shaft was opened to a depth of 70 m, the elevation of the 3rd floor. The production of the mine is unknown. Static leaching was conducted in tanks through the addition of iron sulphides. These, through oxidation, generated acidity capable of shifting the uranium, as well as other heavy metals. The tanks are still visible, and are filled with the leaching residues. They occupy an area of around 1,500 m².