Leave the central piazza in Chiusdino and immediately follow signs to Siena, climbing along the SP 31 “Chiusdino” until you reach the village of La Battellona (roughly 3.5km), where you turn left at the crossroads, leading to the SP 107 “Montalcinello” towards Radicondoli-Montalcinello.
After crossing the Saio River (roughly 5.4km in), go up a short ramp, which has an average gradient of 6% and leads up to a hill with a panoramic view. At about kilometre 8.3, skirting around the small village of Montalcinello, continue along the main road. For a brief stretch you will climb again and then continue up a slight slope to be accompanied by the first geothermal ducts before sliding down towards the foot crossing for Montingegnoli castle (at kilometre 14).
From this crossroads you take the SP3 “delle Galleraie” following signs for Montieri and Follonica. This lovely road serves as a divider between the Merse and Cecina water tables. At kilometre 19.4, turn off to the right to the Galleraie thermal springs, site of the Val di Merse and Petriolo springs, and after 600 metres you will pass into the province of Grosseto, as such the SP3 becomes SP 5 “Montieri”.