The hollow of Oropa, with its specific vegetation and landscape, is the suggestive backdrop to the Sanctuary and the Sacred Mount. The importance of the area was explored in the context of the study realized for the development of the project called ‘Bioitaly’, promoted by the ‘Ministero dell’Ambiente e della Tutela del Territorio’. The latter declared the area of the Sacred Mount a site of regional interest.
The slopes of the mountains encircling the hollow – Mount Mucrone, 2335 mtr., Mount Camino, the highest of the valley, 2388 mtr. and Mount Rosso, 2374 mtr. –  are mainly covered with lavender, alder shrubs and rhododendron, spreading down into the valley, with occasional birch trees to be found in the open fields and abandoned pastures. Certain areas between 1600 and 1700 mtr. of altitude are subject to the growth of mountain pine of anthropic origin.
The area of the Sanctuary is surrounded by forests where the beech tree is dominant, occasionally mixing at lower altitudes with mountain maple and ash, at higher altitudes with laburnum and rowan tree.
The name of the valley, which is particularly rich in water, derives from the homonymous torrent, originating from the Lake Mucrone (1092 mtr.) and flowing partly on the surface and partly underground. The water sources of the area flow into the aqueduct serving the city of Biella. The Reserve is dotted with other small lakes, such as the Mora and the Rosso, as well as with numerous humid zones, classified as high altitude wetlands. The abundance of such zones justifies the need of instituting a protected area to safeguard them.