About 7km east of Bonorva, the Necropoli di Sant’Andrea Priu is an isolated site, immersed in silence and accessible only by a narrow potholed road. It's made up of around 20 small grottoes carved into trachyte rock, some of which date as far back as 3000 BC.
Of the grottoes, the Tomba del Capo, accessible only with a guide, is by far the most interesting. In the early Christian period, three of the main rooms were transformed into a place of worship, and partly restored frescoes from the 5th century survive in two of them. Most striking is the fresco of a woman in the aula (hall) where the faithful heard Mass.