The hill of La Colline du Puy is the highest point in the Municipal District of Aiglun. From the top, at 900m, it offers an exceptional view of the surrounding valleys and peaks. The name of the hill comes from the Latin word which means a small place of prominant, elevated high-ground, and which also led to the use of the words Pic and Pech in other regions.
The hill of Puy and the landscape in the foreground are made up of Valensole's stony and gravelly mixed-rock deposit-composites. These gravel pebbles and stones coated with a natural limestone cement were deposited by rivers during the Miocene period and the Pliocene period (8 to 1.65 million years ago), resulting in formations over several hundred metres in thickness. These rocks are called autochthonous, or indigenous or original rocks, because they have not been moved since their original deposition.
On the other hand, most of the mountains that are part of the other areas of the landscape are described as allochthonous, or non-indigenous rocks (i.e. displaced after their original deposition). Allochthonous, or non-indigenous, rock formations have been deposited on the autochthonous, or indigenous, rock formations. Such allochthonous mountains are composed of sedimentary rocks (limestones, marls, sandstones) which are the result of marine deposits. The sea covered this region throughout the Secondary Era and the first part of the Tertiary Era. During the formation of the Alps, the various layers were crumpled and pleated, broken and displaced, giving rise to these mountain ranges. When the displacement of these masses is significant (several kilometres) it is referred to as a geological-nappe, or a geological thrust-sheet, which is the case for Digne's geological-nappe, geological thrust-sheet.