The Casentino valley is the initial and highest basin of the Arno valley, extending from the sources of the Arno river to the town of Subbiano. It is one of the four valleys comprising the Province of Arezzo. Monte Falterona, where the Arno arises, lies on the northern boundary between the Casentino and Emilia Romagna. On the east of the valley, are the Alpe di Serra and the Alpe di Catenaia, which separate the Casentino from the Upper Val Tiberina. On the west is the Pratomagno, which separates the Casentino from the Valdarno Superiore. Part of the Casentino is included in the Foreste Casentinesi, Monte Falterona, Campigna National Park.
The Casentino is roughly oval in shape, extending either side of the Arno to a width of between 30 and 60 km. The topography of the Casentino is varied, including both river plain and heavily forested mountains. Due to its geographical position and to its history, although it is less than 50 km from Florence, few people know the Casentino well. Since no highways or long-distance railways cross the valley, it is difficult to pass through the Casentino by chance. The mountains that ring the valley encompass the largest forests on the Italian peninsula. This too is a legacy of its long isolation, as is the presence of deer, badgers, wolves and many other wild animal species. Today the forests of the Casentino form a National Park that is among the largest in Italy. These mountains have often attracted great saints: it was here that St. Romuald built his hermitages at Camaldoli, and that less than two centuries later St. Francis of Assisi established the Sanctuary of La Verna, the headquarters of the Franciscan order.
The municipalities of the Casetino valley are:
The larger towns are all located in the Arno valley, the biggest being Bibbiena and Poppi. The villages located on the neighbouring hills and mountains are much smaller. These are Chitignano, Chiusi della Verna, Montemignaio, Ortignano-Raggiolo and Talla.