The town of Piancastagnaio is at 772 m of altitude and it has a population of about 4000 inhabitants. It is in the province of Siena. The bulky Rocca degli Aldobrandeschi overlooks the chief town. Those who love nature can visit the Piggelleto Natural Park in the immediate surroundings.

Piancastagnaio had always been one of the bases from where the Aldobrandeschi pursued their policy of control on the mountain of Grosseto. Both the monks of the Abbey of San Salvatore and the Viscounts of Campiglia had been long contending for the town, that had a huge stronghold, with the noble Lombard-born family of the Aldobrandeschi.
Later, the Republic of Orvieto included Piancastagnaio in 1303 after it influenced the town's politics for a long time.
In the XIV century, also the Republic of Siena began to appear in the story of Piancastagnaio. Siena commenced a harsh fight with Orvieto in the first half of the century. The city of the Palio could annex the territory around 1415 and 1430, also avoiding to be involved into the conflict between the Aldobrandeschi and the Orsini of Pitigliano.
Under the control of the Sienese, Piancastagnaio was became part of the territory controlled by the captain of Radicofani.
Since the first half of the XVI century on, all the Sienese dominions entered of the Grand Duchy of Tuscany. At the beginning of the XVII century, Ferdinand I transformed Piancastagnaio into a feud and ceded it as a marquisate to Giovanni Battista Bourbon del Monte, who built the huge palace outside the walls. The town had to wait for the new territorial organization established by the Grand Duke Pietro Leopoldo of Lorraine to become autonomous. He abolished the feudalism in the ambit of his "enlightened" reforms of the Grand Duchy's organization in the 70's of the XVIII century.