Poggibonsi is a town in the province of Siena, Tuscany, Central Italy. It is located on the River Elsa and is the main centre of the Valdelsa Valleā¦Poggibonsi is a town in the province of Siena, Tuscany, Central Italy. It is located on the River Elsa and is the main centre of the Valdelsa Valley. The area around Poggibonsi was already settled in the Neolithic age, although the first traces of civilisation dates from Etruscan-Roman age, attested by a series of necropolises and by placenames such as "Talciona" or "Marturi".