The hills above Plodio contain rock carvings — engravings cut into the sandstone outcrops — that attest to human settlement in this valley long before the written record begins. The carvings include cup marks, geometric patterns, and animal figures typical of the prehistoric rock art found across the western Ligurian Alps and into Piedmont. The precise dating is uncertain, but similar carvings in neighbouring valleys have been placed in the Bronze Age.
The carvings are accessible on foot from the village via the ridge trails. No formal signage exists, and a local guide or the municipal office can point you toward the most accessible sites. The walk up to the ridgeline takes about an hour and rewards with views across both Bormida valleys and, on clear days, to the Alpine chain to the north and the Ligurian Apennines to the south.