Sasso di San Donnino”, including the source, is known because it is the object of great devotion to San Donnino di Città di Castello, or San Donino, as he is called by the local faithful. A conspicuous number of saints with this name are known, starting with San Donnino di Fidenza, then a bishop of Dijon and one of Grenoble with the same name, two Greek martyrs, one of which from Thessalonica, an Irish holy abbot who died shortly after the 600 as our Donnino (died in 610), and others of minor importance. The scholars of San Donnino of Città di Castello usually draw their information from the ancient Legend of Tiferna (2) and from a manuscript by Alessandro Certini (3). From these documents it can be deduced that Donnino was a companion of the illustrious castellan saints Florido and Amanzio and that after the death of Amanzio, Donnino,
"despising the frequency of men, and every worldly vanity, he began to live a hermitic and solitary life in a cave in a mountainous forest in a place called Robbiano (...) where he lived for a long time in great austerity of life feeding on apples wild and grassy, engaging in prayer and continuous contemplation…” (4).
The hermit, however, was discovered by some peasants intent on collecting acorns, who disclosed his presence, so much so that from that moment many people flocked to him. Donnino, to defend his solitude, was forced to negotiate with his visitors, yes, accepting their help in building a "hut" to be able to live there, but on the condition that he would receive only one or two people every Saturday, accepting from them also something to eat. Only in this way was he able to continue to live his life of prayer and penance for the rest of the years. Tradition attests in various ways that people, however, flocked to visit the saint above all for his thaumaturgical qualities.
The debate among historians to identify the "place known as Robbiano" has not yet ended (5), but the most plausible hypothesis is that the said "hut" was not located near our "Sasso", but in the immediate vicinity of the primitive place where the parish church of Santa Maria del Monte Rubbiano was located. The primitive place of the said parish was recognized by Angelo Tafi in a dilapidated farmhouse belonging to the Gnagnetti family, in Val di Pierle about three km from Mercatale; there was the ancient parish church, which since the seventh century was in the Diocese of Città di Castello and in 1325, with the establishment of the Diocese of Cortona, passed to said Diocese (6). It must be said that, after the seventh century, in an unspecified period, this parish church was transferred to a higher place about 800 meters away from there, where today the Church of S. Maria della Croce is located, and that after the transfer and until 29 January 1781 it was called Pieve di S. Maria e S. Donnino7. Very close to the Gnagnetti cottage there is still today the "fountain" to which, according to historians, the life and thaumaturgical activity of San Donnino is linked, and in whose vicinity there would have been the "cave" or "hovel" in which he lived the holy hermit.
Not to be confused with the source located at the Sasso di San Donnino. In fact, we are dealing with the site called "Sasso di San Donnino", distinct from the places just described, located only a few kilometers away from them, but in the Diocese of Città di Castello, even at present. The site is not attested by any document; the attendance of the holy hermit at the "Sasso" is instead attested by a consolidated popular tradition, which historians tend not to take into consideration. Indeed, it is not easy to unravel the age-old problem relating to the San Donnino residence, perhaps to a certain extent polluted by obvious parochialism. From a lady who has always lived near the "Sasso" and who wishes to remain anonymous, I have gathered a substantial part of this popular tradition. According to his "oral source", San Donnino di Città di Castello would have originated in Romagna (obvious contamination of the tradition concerning San Donnino di Fidenza), would have landed near the ancient Pieve di Rubbiano and at a later time, due to the too many visits from the faithful, he would have moved to the "Sasso" to live more in isolation. In the last years of his life, now ill and close to death, the Bishop of Città di Castello would have come to get him, giving him more comfortable accommodation, in order to end his days (this last addition logically intends to justify the absence of burial at the locality the "Sasso" (8). In fact, a pious tradition links San Donnino to the "Sasso" and is reported in writing by Don Alfonso Marchesini:
“It is said that S. Donnino often went to pray and worked various miracles there. This is confirmed by the fact that the faithful who are sick with kidneys go and lean on that stone and are healed. Sick children brought to this place recover after a few days..." (9).