[1] The river rises in the commune of Guagno south of the 2,496 metres (8,189 ft) A Maniccia, near the boundary of Haute-Corse to the east.

It passes the village of Guagno to the south, and the vollages of Orto and Poggiolo to the north, then flows past Guagno-les-Bains to its confluence with the Liamone.

[2] The Guagno / Fiume Grosso runs through the "Sorru in su" unit of the Liamone landscape.

The Sorru in su valley is similar to the Cruzzini valley, with the same orientation and afforestation, but where the Cruzzini leads into the Monte d'Oro massif, the Sorru in su leads into the Monte Rotondo massif.

The slopes are wooded with holm oak (Quercus ilex), chestnut (Castanea), maritime pine (Pinus pinaster) and laricio pine (Pinus nigra), while the rocky ridges descending from the Monte Rotondo massif are bare.