East of the Saline River (or Imera South) stands the mountain group Erei Mountains, a complex orographic terrain, consisting of isolated hills and hilly nature of sandstone and sandy-calcarenitico, aligned from north to south, between Enna and Caltanissetta. They culminate in Mount Altesina, which feeds the main source of the river Dittaino. Taking account of the relief Erei are part of the watershed between Africa and the Ionian Sea.
Guard and the tops of the most distinctive central part of the island lies at the heart of Sicily in approximately the point of contact between the three geographical regions in which administrative action in the Middle Ages was divided Sicily (Val di Mazara, Val di Noto, Valdemone) there were such until the end of feudalism (1812) and in close contact with the dorsal nebroidea (north-east), high in chalky solfifero (south-west).
Erei Mountains are a mountain group located in central Sicily, mainly falling in the central and northern part of the Province of Enna.

The Erei are of calcareous origin, and do not reach great heights. The area was once one of the world's most important with regard to the extraction of sulfur, today witnessed the interesting mining parks scattered throughout the territory, including the Mining Park Floristella Grottacalda and is the largest.
The mountain is dotted with lakes (including Lake Pergusa most important of which for the rich fauna of birds is home of the first special nature reserve established in Sicily and Lake Pozzillo, the largest reservoir of the island) and nature reserves.
Because of the succession of rugged hills, the population and population density are both small, not more than 200,000 are residents. Inside, however, there is the largest Italian city placed above the 900 m above sea level and the provincial capital of Europe's highest, Enna, where he focuses around one sixth of the population erea.

The mountain is crossed by a motorway, the A19 Palermo-Catania, from a railroad of the same walk. Most other roads that cross the region is full of twists and turns, due to the accidental land, geologically unstable.
The natural heritage of the Mountains Erei is one of the best preserved and richest island. City of art are Enna, Piazza Armerina and Nicosia, archaeological excavations of the citadel are the primary indigenous Hellenized Morgantina with the agora and the greek theater, the Villa del Casale, UNESCO World Heritage Site for its priceless Roman mosaics, l 'Roman archaeological Centuripe with prestigious archaeological museum. This testifies to the ancient settlement of the geographic area.