It was long believed that the Pranu Is Calas archaeological area constituted a significant cultural complex of prehistoric age, formed by an intentional concentration of menhirs. Later, an archaeological investigation revealed the presence of wall structures arranged with some regularity but reduced to only the base lari; the so-called menhirs constitute elements of frame masonry in this. Ceramic finds allow a date to the Roman imperial age. About 200 meters away on a rise is the protonuraghe called Nuraghe Is Calas. It is a semicircular structure with a chamber; it is built with large and medium-sized ashlars of quadrangular and polyhedral shape, arranged in irregular wall larii. The position of the entrance and the thickness of the wall faces are not legible due to the degraded state of the structure.
