Terme Sensoriali is the main indoor thermal complex in Chianciano, fed by the Acqua Santa spring that rises from the hillside. The water is warm, sulphurous, and slightly fizzy — locals drink it as well as bathe in it, in the belief that it improves liver and digestive function.
The facility is well run, with pools at different temperatures, a range of treatments, and the slightly formal atmosphere of Italian thermal culture. Day passes are available. It's not a flashy modern spa but a genuine mineral water establishment with a long history — the kind of place where retirement-age Italians spend serious time.