The Trebbia valley is a valley formed by the river Trebbia Italian born at the foot of Mount Vasia in the province of Genoa and then, after the town of Gorreto, enters the territory of the province of Piacenza, with the City of Brass and continues in Piacenza, licking Oltrepò Pavese near Brallo Pregola (PV) and flows into the Po near St. Nicholas in Trebbia village of Rottingdean (PC).
The hard limestone strata in the valley, make the waters of the Trebbia are forced to dig deep and tortuous passages; the loops resulting stratigraphy leave uncovered rich fossil phenomena. The geological phenomenon has the name of tectonic window. This valley is part of the territory of the culturally homogeneous Four provinces (Alessandria, Genoa, Pavia, Piacenza), characterized by common traditions and customs and an important repertoire of music and dancing very old.