Sasso Fratino is an integral nature reserve - the first to be established in Italy (1959) – and thus not the slightest alteration may be made within this area. Protection of nature is considered in its entirety (species of plants and animals, rocks, soil and water: everything) and no forestry activities are undertaken, i.e. the plants are not cut and reproduce naturally, trees are left where they fall and are attacked by fungi, insects and microorganisms that promote their decomposition. The aim of the reserve is to ensure integral conservation of a rare forest for scientific purposes, maintaining the natural equilibrium and making it as far as possible similar to the virgin forests that covered Europe thousands of years ago. This area of 764 hectares falls almost entirely within the municipality of Bagno di Romagna and stretches from the steep north-eastern slope of the ridge dominated by Poggio Scali (1520 m) down to the road that leads from the Lama Forest to Ponte alla Sega (650 m) and the "Fosso delle Macine", which is a practically impenetrable gorge in the heart of the National Park of the Casentino Forests where the complex morphology of the land has always limited the cutting of timber, grazing and ploughing. In 1914 this area of forest became state property, together with the central area of all the Casentino Forests. In 1959 it was decided that free access would be denied to a portion of about 110 hectares; this decision marked a first concrete step in the protection of the environment. Subsequently a number of decrees enlarged the area of the Integral Nature Reserve of Sasso Fratino, which now comprises 764 hectares.
The wood, which has a number of centuries-old trees of colossal size, consists largely of spruce and beech trees that are mixed with many other tree species (sycamore, maple, hornbeam, mountain elm, linden, ash, yew). Its wealth of genetic variability does not stop with trees, to the extent that it was awarded a diploma for its highly precious biological value by the Council of Europe in 1985, a recognition of its worth that was later renewed twice again.