Province of Genoa
From its source the river flows towards north-east for until it reaches the Po just to the west of Piacenza. The Alta Val Trebbia ("High Trebbia Valley") includes the valley down to Bobbio. It straddles eight "comuni" of the Province of Genoa: Torriglia, Rondanina, Propata, Fascia, Montebruno, Rovegno, Fontanigorda and Gorreto. Each of these contains numerous hamlets, some on the river, most on the slopes. Gorreto is on the Ligurian side of the border with Piacenza province.