Forni Valley takes its name from the glacier that dominates it, one of the giants of the Italian Alps with an area that still exceeds 10 km2, counted among the best witnesses of past and current climate changes. Forni Glacier is now clearly visible if you reach the Cesare Branca Hut at 2493 m above sea level. It was until 2015 one of the very few valley glaciers of the Italian Alps with composite basins, also known as a “Himalayan” glacier, and represented the largest valley glacier on the southern side of the Alps. 
The head of Forni glacier is delimited by a rocky ridge which forms part of the classic and popular mountaineering itinerary known as the "traverse of the 13 peaks", where peaks like San Matteo (3678 m) and Tresero (3602 m) stand out. 
In the recent past, three accumulation basins fed the wide glacier tongue. This reached the position of the dam managed by A2A for the production of hydroelectric energy at about 2100 m a.s.l. 150 years ago and over a century and a half it has retreated by over 2 km in length. In 2020, the terminus stood at an altitude of just under 2600 m. 
Currently only the central accumulation basin is still connected to the ablation tongue; this is because in 2015 the eastern serac that connected the eastern basin with the tongue completely disappeared, following collapses, and in 2018 the same fate was shared by the western sector, now no longer communicating with the ablation tongue. 
The meltwater from Forni glacier is firstly collected at the A2A dam through a dense network of canalizations and then reaches the Cancano basins and contributes to the production of hydroelectric energy. Through the e-bike cycle paths we can observe many basins and dams as evidence of the amount of water that in Lombardy is stored and used for energy production. It is no coincidence that this region represents 28% of the national hydroelectric power! 
Instead of an ice tongue, the Forni valley now houses the Frodolfo stream, fed by glacier melt water and characterized by loops and meanders, and a rapidly rising larch and spruce forest. The oldest plants that now populate the forest in the valley have been analyzed with dendrochronological methods and are found to be around 120-130 years old; the youngest, present in the plain in front of the current glacial front, are 2-5 year old specimens, and clearly testify to the speed with which the vegetation is colonizing the area freed by the "white giant" of the Stelvio park! 
Observing the Forni Valley and the glacier from the terrace of the Branca refuge, the large lateral moraines built by the glacier in the Little Ice Age are clearly visible, the so-called roches moutonées, rocks smoothed and rounded by the glacier when it flowed over them, many of them found only in the last twenty years, and the small lake of Rosole, a moraine basin now fed by the meteoric water and snow melt. 
To visit the Forni Valley and reach the progacial plain, it is possible to climb from the driveway that connects the Forni Refuge (at 2100 m) to the Branca Refuge (at 2493 m) and from there take a well-marked path, to be done on foot, which through a spectacular Tibetan bridge will lead us to the terminus of the glacier. The path can be taken after the Rosole Lake. Alternatively, we can choose to take the lower glaciological itinerary that starts from the A2A dam and continue along the Forni stream in the long deglaciated valley. This second possibility allows you to better appreciate the naturalistic peculiarities of the area in a path not accessible to jeeps and off-road vehicles.