The Sasso della Dolorosa (682 m a.s.l.) is a peak belonging to the small mountain range of the Monti Pisani; from its top start the watershed lines that form the borders between the valleys of Vicopisano, Buti and Calci. It is particularly known for the fact that the Florentines, engaged in the war against Pisa, built a triangular-plan fort in 1496, with the dual purpose of isolating the Verruca fortress and better controlling the situation in the three surrounding valleys, the position strategic position of the top, in fact, being on the intersection point of the already mentioned watershed lines, it allowed a great freedom of action.
However, this outpost was most likely built hastily, as only a small amount of debris has survived to this day. (cited on Wikipedia)