The Nature Reserve lies in the east of the town of Rondissone, and covers a total area of 190 hectares, at the border between the Provinces of Turin and Vercelli and in the Municipalities of Mazzè, Rondissone, and Saluggia. The reserve protects the stretch of river Dora Baltea and the territory surrounding it between the road Padana Superiore and the highway A4. The area, eroded by the river over the millennia, creating a characteristic large river depression, lies at a lower altitude with respect to the surrounding alluvial terrace. The landscape is characterized by large gravelly shores and beaches and by interesting woodlands with riparian vegetation (poplars, willows, alders, etc.), by poplar groves or locust tree groves surrounded by sowable lands and meadows. Moreover, within the reserve there are also some beautiful farmsteads with architectural features between the typology of the Canavese area and the one characterizing the plain of Vercelli. The name of the reserve derives from the old mill present in the area, now under repair. The area is crossed by the cycle facility no. 7 of River Po Park, that in this area crosses a canal thanks to a special wooden bridge inaugurated in 2005.
Mulino Vecchio Special Nature Reserve is safeguarded not only by the establishment law of River Po Park, but also according to the regional law no. 47 of 3rd April 1995 "Norme per la tutela dei biotopi", the Decision 85/338/CEE of 27th June 1985, and the Directive 92/43/CEE of 21st May 1992, since it has been considered as "ecological entity of great interest for the conservation of nature" and therefore subject to the environmental-landscape regulations according to law 8th August 1985, no. 431 and the European regulations, recognizing it as SCI – Site of Community Importance (code IT1110050).