The Franciscans settled in Barbagia at the beginning of the 17th century in the Logotza district , the southern part of the current town of Fonni , a village set about a thousand meters above sea level. On lands donated to them in 1610 by benefactor Stefano Melis, they built a church and convent dedicated to the Trinità. Both had typically Franciscan, very simple architecture: the first with a single, barrel-vaulted nave with three chapels on each side; the second with a well in the centre surrounded by a quadrilateral cloister. In 1702 on the initiative of Father Pacifico Guiso, the friars began work on a new sanctuary, grafted onto the pre-existing church and dedicated to the Vergine dei Martiri. The ambitious project, which provided for an upper sanctuary and an underlying crypt, was entrusted to Milanese stonemasons and workers (and was completed four years later). To them we owe the floral and exuberant artistic language, then in vogue in the European capitals.