For 10 points, identify this chief river of Cisalpine Gaul, the primary waterway of Northern Italy.
One city in this river's valley contains Monte Leoni, a chief site of the Terramara culture, and this river was located south of the lakes Benacus and Verbanus. One name of this body of water, Bodincus, means "bottomless," and supposedly Phaethon crashed his chariot into this river, which was identified with the (*) Eridanus. Passing through Liguria as well as the city of Augusta Taurinorum, cities in its valley include Modena, Parma, and Turin. For 10 points, identify this chief river of Cisalpine Gaul, the primary waterway of Northern Italy.
One city in this river's valley contains Monte Leoni, a chief site of the Terramara culture, and this river was located south of the lakes Benacus and Verbanus.
Po River [accept Padus, prompt on Eridanus early] 