According to tradition, in 1215 Saint Francis received the Hermitage of mount Subasio as a gift from the Benedictines. 
Between 1217 and 1221, Saint Francis wrote the 'Rules of life in hermitages', a code of behaviour to be observed by monks wishing to retreat in silence and peace. 
From 1378, first with Friar Paoluccio Trinci, who started the Osservanza movement, then with his follower Saint Bernardino of Siena (1380-1444), the first improvements of the sanctuary were made, with the construction of a humble dormitory, a refectory and the small church nearby. 
The altar of the 15th century church has a  Crucifixion from the 15th century Umbria-Siena school. There is an interesting small stained glass window of French origin on the back wall (14th century); opposite is a cabinet with mementos of the saint. An iron gate leads to the early church, where on the altar you can see the cross that the saint wore when he was evangelising; behind is a fresco with  Madonna with Child and Saint Francis, attributed to Tiberio d'Assisi (early 16th century).
An interesting walk through the woods starts with the bronze statue by Vincenzo Rosignoli,  San Francis liberating the doves  (1882), and leads to an extremely old oak tree on which the birds are said to have gathered to be blessed by Francis. 
The path takes you to Beato Leone grotto; the grottoes of the saint's other companions are past the stream. Further on are the grottoes of San Masseo and Beato Rufino.
Today the community of monks residing in the sanctuary welcome all those who wish to join the Franciscan experience in full respect of the Rule of life in the Hermitages.