The Nature Reserve covers a large part of the village of Sixt Fer à Cheval. With its 9200 hectares it is the largest in the Haute-Savoie region.
Over and above the actual size of the reserve, it is the magnificence of the territory over which the reserve is spread which makes it really exceptional.
The limestone massif that forms the Haut Giffre is subject to intense erosion which creates a sharply contrasting relief where a mix of marsh land, forest, pastures, cliffs, alpine karst, glaciers and glacial cirques can be found.

The large altitude range, the contrasting geological landscapes and the biographical position of the massif have allowed development of a very rich and varied flora and fauna...
Some 800 plant species have been noted with some quite remarkable examples such as the Sabot de Vénus (Lady’s Slipper), the Chardon Bleu (thistle), the Ancolie des Alpes (alpine columbine) or the Lys Martagon (Martagon Lily).