At Fonni's highest point is the imposing 17th-century Basilica della Madonna dei Martiri, one of Barbagia's most important baroque churches. Surrounded by cumbessias (pilgrims’ huts), it’s famous for a revered image of the Madonna that’s said to be made from the crushed bones of martyrs. In June it's the focus of Fonni’s two main feast days, the Festa della Madonna dei Martiri on the Monday after the first Sunday in June and the Festa di San Giovanni on 24 June.
Outside the church a couple of trees have been curiously transformed by sculptors into religious scenes, notably one showing the crucified Christ and the two thieves.
