The small turreted village near the upper Val d'Egola that Leonardo depicted on map RLW 12278 with the name of "sancto stefano", between Montaione, Barbialla, and Collegalli, must be identified as the castle of Santo Stefano, a small town of medieval origin, of which traces remain today in the homonymous hamlet of the municipality of Montaione. The church of San Bartolomeo a Santo Stefano belonged to the ancient community of Santo Stefano, and still stands today along the Maremma road, about four kilometers northeast of Montaione.
The castrum of Santo Stefano is mentioned for the first time in 1182, on the occasion of the actual transfer of the castle with all its appurtenances, including inhabitants of the castle and the rights over them, by the local lords, the Guascone brothers, Ranuccio and Benno, the latter of which was holder of the parish of Chianni. The three men, with the consent of their father Ugolinello, sold the castle to two personages, Astone and Oddone di Rolandino. The deed of sale was drawn up in the villa of Varna, under a porticoed building. We do not know the protagonists of the sale of the castle of Santo Stefano, however the men involved seem to have been connected to the lesser aristocracy of these places. Moreover, Varna, the place where the deed was drawn up, was, like the castle of Catignano, within the orbit of the Valdelsan possessions of the Cadolingi. Indeed, we find exponents of the counts of Fucecchio active in this area until the end of the 11th century, together with members of local families such as the Ghisolfi and the de Callebona. Therefore the place called "sancto stefano", mentioned among the assets donated by the Cadolingi in 1034 to the Fucecchio abbey of San Salvatore, is to be identified, in all probability, with the castrum Sancti Stefani of the 1182 document.