The Nature Reserve of the Valley Sosio affects the municipalities of Burgio and Bivona.

The reserve, among the most fascinating of the region, is known around the world for its great palaeontology; the fossil-rich limestone blocks of macro and micro marine faunas dating from the Permian Era, the last period of the Paleozoic Era.

  The Sosio river starts in the Sicani Mountains and after a small stretch enters into a canyon called “listi d’u firriatu ”, a deep gorge 8 km long and 300 meters deep, surrounded by forests of oak trees.

The canyon is watched by two rare birds of prey: the Egyptian vulture and the golden eagle, as well as ravens, hawks, buzzards, and the Sicilian woodpecker.

Reachable from Agrigento: SS 115 to Sciacca, exit at Ribera, then take the SS 386 for Burgio; about 2 km before San Carlo turn right at the foot of the mountain, at the ruins of Cristia Castle.