Santuario delle Pietre Grosse

The Santuario delle Pietre Grosse takes its name from the numerous boulders situated near the Riale stream, a right-bank tributary of the Sesia, at the start of the road leading up towards Pizzo and the Meggiana Mountain Hut.

If you look closely at the hillside behind the Sanctuary, you will notice just how many boulders there are. In fact, starting from the Sanctuary and heading uphill, you will see that the boulders are present in great numbers, before decreasing considerably in size and number as you approach the road to Meggiana.

The boulders are composed of eclogitic mica schist and green schist. These boulders, some of which are as large as ten metres, are the result of a massive landslide that, in the 17th century, affected the north-eastern slope of the final stretch of the ridge running from Monte Bò in Valsesia to Pizzo and then descending towards the valley floor. The exact point where the boulders broke away is not clear today, since, if – as historical documents state – the landslide occurred in the 17th century, enough time has now passed for vegetation to have obscured the traces. It is possible to hypothesise a potential area where the boulders broke away: 700 metres upstream of the Sanctuary, with a front at least 300 metres wide. In this hypothesised area, the gradient is steeper than in the surrounding areas, suggesting that this area could represent the niche from which the boulders broke away.