The Rocca Aldobrandesca is the unmistakable symbol of Piancastagnaio, an imposing fortress of medieval origin, mentioned for the first time in 1194. Of the original walls, in addition to the Rocca, three other towers and several gates remain visible, including the Main Gate (next to the Rocca), Porta Romana, Porticciola and Porta di Voltaia. Palazzo Bourbon del Monte, built in 1603, is a remarkable example of seventeenth-century architecture.