In Briaglia, in the Casnea locality, a megalithic area dating from the period of Ligurian occupation of the Po Valley, probably originating in the Bronze Age, was discovered in 1970.

The area was investigated by archaeologist Ettore Janigro d’Aquino, who initiated a series of excavations that uncovered evidence of a previously unknown people, according to him the Liguri Bagienni tribe. The excavations brought to light several stones showing anthropomorphic and zoomorphic figures, definable as megalith-menhirs. A dolmen, a half-moon cavity carved into the marble by human hand, containing two very deep shafts, used as a burial chamber, preceded by a 30-meter-long corridor, also came to light. The most striking aspect of the discovery comes from an archeoastronomy finding at the winter solstice, the sun’s rays penetrate directly into the chamber, creating a peculiar play of light.