On the top of a steep hill in the final part. This is the first impact on Osilo. From the summit we can understand why in the mid-13th century, the Malaspina, a family from Lunigiana, built a castle using the remains of some older buildings from the Roman era. They preferred this hill, the outermost of the Tuffudesu range, because it was not important what was seen from the castle, but from where the fortification was seen. And the best view is from the bottom of the valley and along the roads that led to Sassari where there was the first village of Ogosilo around the small church of S. Barbara (today S. Giovanni). The Malaspina built the castle when the fate of the Giudicato of Torres was now sealed and when other lordly families, the Doria, were already dividing up the territory around the new municipal entity of Sassari. On the summit the lords set a new way of living but the name of the older village was preserved. The stately form of the settlement is still preserved in the organization of the streets of the old town, which represent autonomous lines of defense of the fortification. And higher up is the castle, with a trapezoid-shaped floor plan and a width of nearly 1,000 square meters. The earliest documentary record of the castle is contained in the Statutes of Sassari (dated post-1272 ). Most of the information about the castle concerns the period after the marquises’ rule since in 1326, following a phase of bitter confrontation with the Aragonese, they were forced to cede control to the Catalan king. But by now the new center of Osilo had established itself as the territorial coordinating center confirmed in 1343 with the creation of the ‘barony’ of the same name, which included the three districts of Montes, Figulinas and Coros, entrusted to the government of a royal vicar. Osilo’s leadership was perpetuated even in the next feudal phase marked by the lordship of the De Ҫentelles, who placed in the fortified village the capital of one of their vast territorial appurtenances. Outside the walls, beyond today’s Sanna Tolu Street, the church dedicated to the Virgin (Immaculate). It was in this same church that several centuries later, in 1772, the Collegiate Church, that is, the chapter union of priests, was born. The institution, which remained until 1872, represented the culmination of a long economic process and became a stimulus for the construction and beautification of other churches. There were more than forty in the territory in the first half of the 19th century.
