The fortification was built by the Malaspina family (first mentioned in the Sassaresi Statutes 1272) but their name associated with the castle does not appear until 1301.
Pietro Alighieri, in an annotation in his father Dante’s work (The Divine Comedy), reports the fact that the castle would have been brought as a dowry to Corrado Malaspina by Orietta, daughter of the judge Mariano, suggesting that the fortification already existed before the rule of the marquises.
In fact, the role and function of the castle is understood precisely in the historical phase of disintegration of the Giudicato di Torres, when several Italian noble families managed to create autonomous territorial spaces equipped with a castle.
These constructions represented the emblem of their political, economic and military success.
In Sardinia among these families we find the Doria, Della Gherardesca, Spinola, Visconti and precisely also the Malaspina.
It is in this context that we understand Alighieri’s annotation, if we consider that his father was a guest several times of the Malaspina family in Lunigiana.
The marquises, then, taking advantage of the institutional political chaos of the last quarter of the 13th century, succeeded in the feat of taking possession of the second port of the giudicato (Bosa), although it was later ceded to Arborea in 1317.
The castle they controlled for the longest time, with a more articulated seigniorial project, was precisely that of Osilo, located behind the nascent municipality of Sassari.
