This large woodland area of pure nature and a wide range of biological evidence i situated at the centre of the Colline Metallifere (hills). The reserve includes two homonymous regional forestry complexes, an important communal site and an important regional site.  Vast forest and scrubland, nature at is purest and bio-diversity are crossed over by a tight net of torrents of which the Sterza  and the Trossa.  All of these attributes go to make this wilderness the most important in Tuscany.  Different habitats are home to flora and fauna elements of the most rarest and ecological kind, even if distinguishing elements are of wide ophiolite appearance with typical endemic flora and very interesting mineralisation.

The forestry groundmass constitutes the  dominating element of the area, extending over a vast hillside area which is mainly of rock sediments.  The different aspects  of morphological landscapes, the excellent state of conservation of the habitats, nature at its best and notable places of bio-diversity all contribute to the great importance of the landscape and nature.

In the Caselli area, there is a complex net of footpaths, which enable you to discover uncontaminated and particularly suggestive areas.

Travelling along the roads, the footpaths and the old tracks which line this vast territory in front of views which leave you speechless, you can feel natures rhythms, mans greatness, and pervade an area more or less intact.