The union of the two rivers, which receives the waters of all surrounding hills, reflects in a certain way the junction of three territories historically and geografically diverse: Mount Amiata, Siena and Montalcino, and Maremma.
The territory closest to Pozzuolo was intersected by the important roadway that joined the Etruscan centers of Roselle and Chiusi. The ancient roadway traveled up the Ombrone Valley and followed, beyond the rivers’ confluence, the whole Val d'Orcia Inferiore beyond the hillsides of Bagno Vignone. Once crossed the Val d'Orcia Superiore, the roadway reached the Chiana land. During the Middle Ages, the link between the Maremma and Val di Chiana took a detour after the junction of the two rivers, in order to head North towards the hills of Montalcino. Once crossed the Francigena Way, the roadway continued into the Valle dell'Asso to reach the Chiana land beyond the hills of Montisi and Trequanda.

Pozzuolo was surely a medieval castrensian settlement favored by an optimal geografical position, which was very particular due to the junction of four dioceses. Closeby, the river Orcia and the ditch Trisolla marked the border with the dioceses of Arezzo and Grosseto.
Until the first half of the fourteenth century, Pozzuolo was the dominion of noble families, presumably the Squarcialupi family. In 1361, when the town nobility took possession of wide land areas, it is certain that the castle passed from Longaruccio Squarcialupi to Giacomo Tolomei together with the castle of Porrona. The castle is one of many properties - fortresses,
lands and private castles - for which the Comune of Siena issued a reform order on the 9th of May, 1438.