BONORVA — In the volcanic highlands of central Sardinia, a labyrinth of rock-cut chambers has kept watch over the dead for six thousand years. Known as domus de janas, or “houses of the fairies,” these tombs are carved directly into trachyte and basalt outcrops, and more than three thousand of them survive across the island. The largest and most storied lies at Sant’Andrea Priu, near Bonorva, where visitors can walk straight into a chamber first used by Neolithic islanders around 4000 BC.