Chronologically this unit is attributed to the upper Triassic and Jurassic, while in palaeogeography it's considered as the innermost part of the Briançonnais zone, an area of the Penninic nappes of the Alps.

[9] In 1904 the geologist Gaetano Rovereto, in his work Geomorfologia delle Valli Liguri, mentioned the Castellermo for its craggy peaks, with horrid and distinctive shapes (cime dirupate, orride e con forme caratteristiche).

In particular on the slopes nowadays included in the municipality of Vendone, in a place referred as "Tre Pe", there was a dolmen presumably built by the Ligures,[11] which unfortunately was destroyed by some youngsters of the village in the early post war years.

[13] The same name Castellermo, a short form of Castello dell'Eremo (in English Castle of the hermitage), is connected to an ancient tradition stating that saint Calocerus lived there as an hermit.

In the Casone dei Crovi, an old building close tho the summit of mount Peso Grande, at the end of 1943 some partisans led by commander Felice Cascione composed the famous song Fischia il vento,[15] which was executed in public for the first time in the nearby village of Curenna.