In the woods North of the town of Mergozzo, at a place called Groppole, which can be reached on foot from Bracchio, stands a curious megalithic structure known as Ca d’la Norma.
It is composed of a small elliptical-shaped chamber, bordered by large dry-laid stones and covered by a large erratic block on the top of which two cups and a groove are carved.
There is no certainty on the dating of the structure, but scholars deem that the building should certainly be attributed to the vast and varied megalithic culture.
Other similar remains, such as the massive wall with internal chambers known as the “Muro del Diavolo” (Devil’s Wall) in Crodo-Arvenolo and the circles or rows of stones coupled with massive walls with internal chambers in Montecrestese, at Castelluccio and Croppola, can be seen in the territory of the Ossola Valley, long ago inhabited by the Leponti tribe.
Another unusual stone structure has recently been discovered: in the shape of a lithic shrine, it is also located in the terraced woodland west of the town, not far from Ca d’la Norma.
Another element of pre-protohistoric sacredness is associated with the megalithic structure at Groppole di Mergozzo: a boulder with cups carved into it. Both phenomena are thought to be traceable to ancestral forms of worship of rock and mountains.