The Sierra Montgrony is formed by an alignment of mountains which form the eastern extension towards the natural Moixeró, circling along the southern Ribes Valley. Overall space remains an eminent nature forest fragments of oak, beech, pine and in good condition.
The area covers an area of 3512.0 hectares, of which only 620 are located in the area of ​​Berguedá, specifically in the area of ​​the municipality of Castellar de N'Hug. The rest of the area is included within the Ripollès.