With a dimension of 84 mts length and 35 mts width but especially with more than 5.000 engraved figures on its surface the Rupe Magna is the biggest engraved rock in the Alpine range. The engravings can be dated to the end of the Neolithic Period (4^th-3^rd millennium B.C.), to the Bronze Age and to the Iron Age (1^st millennium B.C.). Numerous themes like geometric forms, anthropomorphic figures in a praying position, armed warriors or animals are represented. Still a mystery are the numerous cup-marks („Coppelle“).

The practice of rock engravings is well known for the Alpine zone. In northern Italy rock art can be found from the Aosta Valley in the West to the region of Veneto in the East. The region of Lombardy has two valleys with a strong concentration of rock art, the Val Camonica and the Valtellina. Both show a lot of similarities but on the other hand they have even highly local characteristics. Most of the rock engravings were made with a technique known as “martellina”. By picking the rock with a stone tool small circular shaped pieces chip off the rock until the figure is drawn into the surface. Another possibility is the “graffito” technique, but this was  not used on the Rupe Magna. In that case the figures are engraved by intense scratching of the surface with a pointed instrument.

In Valtellina the most important site with petroglyphs is the one of Grosio. Next to the impressive amount of rock engravings on the Rupe Magna, discovered in 1966 by Davide Pace, about fifty small sectors with rock engravings have been found on the nearby Giroldo Hill. The Rupe Magna owes its morphology to the action of the last ice age in Valtellina. The glacier erosion has shaped the Rupe Magna itself and even flattened its surface. On the Rupe Magna man can find various figures like anthropomorphic ones, so called „oranti“ (prayermen) and armed ones, furthermore  animals, geometric figures and cup marks.

The petroglyphes are mainly dated on the principle of comparison with objects out of archaeological excavations and stylistic analysis of the figures themselves. Hence the rock engravings were realized between the end of the Neolithic (4^th millennium BC) and the Iron Age (1^st millennium BC). In the years of 1991 to 1995 the petroglyphs of the Rupe Magna were completely mapped and documented. It could be shown that the more than 5.000 engravings are scattered all over the surface of the Rupe Magna which is therefore one of the largest rocks with petroglyphs in the whole Alpine range.

To complete the overall picture of rock art in Grosio even the sections discovered in 1970 by Davide Pace on the Giroldo Hill have to be mentioned again. On the Giroldo Hill, which is located north of the Castle Hill, more than fifty sections with petroglyphs are identified so far. Of particular interest is the one called “Roccia degli Armigeri”, a rock with a various number of anthropomorphic figures armed with shields and lances.