The public thermal bathing facility below the village — known as the Piscina Val di Sole or Terme Bagno Vignoni — offers what the historic pool in the piazza does not: the actual experience of soaking in the thermal water. The pools are fed by the same underground source that fills the piazza, at temperatures around 39–42°C, and sit in the valley below the village with views up to the old stone buildings above.
This is not a spa complex in the resort sense — it is a relatively simple outdoor facility, but the setting in the Val d'Orcia landscape and the quality of the water make it genuinely restorative. The sulphurous spring water is traditionally credited with therapeutic properties for skin and joint conditions; you can judge that for yourself. Open year-round; winter bathing with steam rising around you and the valley empty of tourists is the best time to visit. There is a small charge for entry.