Its uniqueness is an inner road, entirely lit up, that runs along its sinuous length, making it a unique case in Italy and a rarity in the world. The San Giovanni grotto, commanded by Mount Acqua (540 m) on the east and by Punta San Michele (900 m) on the west, is located in the territory of Domusnovas, in the Iglesiente, three kilometres from the town. It opens at the end of a road that leads to the feet of the mountain. It is named after a chapel dedicated to the saint, which used to be protected by the grotto up to the 1800’s. It was later destroyed to make room for the road, used to transport material from the sa Duchessa mine.