At Castel Castagnaio, on a high ground at 800 meters above sea level, there is an ancient Etruscan temple, on which was then built a Roman temple and finally, around 1000, on the foundations of the latter an ancient castle owned by the Guidi counts, of which there are now few suggestive ruins. The castle, like others on the Alpe di Serra (Montefatucchio and Serra) served as a military outpost for the control of transit routes, in this case especially the one towards Mugello, and was usually guarded by a few men. The chosen place also made communication easy, being ¿a vista” the other castles of the Guidi of the area such as Porciano and Stia.
In addition to the roads, the waterways (Arno and tributaries) played an important role both for the water supply and especially for the various mills that were there, perhaps linked to the castle, and which has remained in the place name (Le Molina and Molinuzzo)while the village owes its name to the surrounding large chestnut woods.
After the battle of Montaperti (Siena) in 1260, where the Guelph Florence was defeated by the Sienese, both the castle and the mills were largely destroyed by the victors Ghibellines, even if the castle survived good or bad until 1440, when it appears
