The Forra del Cellina Natural Reserve was set up in 1998 in an isolated area of Western Friuli. It is managed by the Dolomiti Friulane Natural Park: 304 hectares of steep walls and rocks smoothed by the rush of the waters, it is the largest canyon in the region and clearly one of the most extraordinary in Italy. In its thousand-year rush down to the valley, the Cellina creek, with its vigorous emerald colour flow has slowly carved the hard layers, around which an extraordinary microcosm has emerged. This documentary film, besides showing the geomorphologic, vegetation, wildlife and water characteristic of the Reserve, describes the historically important anthropological issues which are linked to the building of a series of hydroelectric installations and a spectacular road dug in the rock, which was once the only contact with the outer world for these small mountain villages. The thousand-year isolation of these places in Valcellina has contributed to preservation of the most characteristic natural and human aspects of this spot in Friuli.