It is said that St. Francis of Assisi himself did designate and choose the place where the first Franciscan Convent, the Convento Castrum Plani Castagnarii, was then built. The very first location where the Convent was built, named the “Old Place”, turned to be extremely inconvenient, not only for the inhabitants of Piancastagnaio, but also for the friars themselves, who, due to the distance from the village, risked to die of starvation in the winter. It was therefore decided to move the Convent in a place closer to the Castle: it was then that the Convento San Bartolomeo and its adjacent Church were built in Piancastagnaio. The old place where the Convent was originally located was granted by Count Ildebrandino degli Aldebrandeschi, son of Count Guglielmo of Sovana and Pitigliano. On September 5, 1276, Mgr. David Dandini, Bishop of Sovana, wrote a pastoral letter to the community of Piancastagnaio, urging them to contribute to the construction of the Church of the new Convent, only a few hundred meters away from the majestic Rocca Aldobrandesca. It was Monsignor Dandini himself who laid the foundation stone and, on that very same occasion, the “Castagnone” was also planted. Even today everyone can admire the big chestnut tree at the entrance of the Convent. The new Church was consecrated in 1278. In the beginning only about 10 friars lived at the Convent, whose structure was by them managed to be preserved thanks to the donations given by the pilgrims and the help given by the local farmers.