News of the curative power of Chianciano's water became well known during Roman times, as Horace visited the area on the advice of his physician during the 1st century BC.

In 1993 bathhouse columns and an enormous tile-paved swimming pool have been excavated as part of a major spa complex unlike anything else ever found in the Siena region and one of the largest in Italy, and consistent with Horace's description.

Its position close to the Via Francigena (the medieval main connection from Rome to France) fostered its development, and Chianciano reached a degree of judicial autonomy by 1287 when it established its own statutes.

In contrast to this is the modern quarter, the Terme, whose nucleus has grown around the thermal springs and stretches northward in a crescent shape along the Vale della Libertà towards the older city.

The Church of the Immacolata, restored in 1588 after the Florentine conquest of Siena, once housed the paintings Annunciation by Niccolò Betti, Holy Family by Galgano Perpignani, and a fresco of Madonna of the Peace attributed to Luca Signorelli.