From the main piazza in Sarteano take the road towards Radicofani. Turn left at the first junction, after the sports field, towards San Casciano dei Bagni. The road with its various ups and down goes past the Il Biancheto area (reaching Grotta Lattaia, a magnificent natural cave, which can be visited if arranged in advance with the Cetona Museum, the Belverde Natural Archaeological Park Services Centre, an interesting archaeological site, and reaches the Cancelli pass along a mostly uphill road: there are two parts that aren't particularly long yet are demanding, 14 and 12 percent gradients respectively.
From here (9.8 km from Sarteano), having passed the Cancelli services, carry on downhill towards San Casciano dei Bagni (15 km from Sarteano). Return to the road for Sarteano-Monte Cetona (SP 89 Montagna di Cetona) and, after 700 metres, veer left following the sign for Podere Armatello: having started along the unpaved road, ignore the next deviation for Podere Armatello, carrying on along the main track (great views over Radicofani and Monte Amiata), which after 1.5 km starts to descend steeply.
After 4.9 km from the start of the dirt track, you reach a large crossroads. Turn right uphill and, after 900 metres, the road turns left (ignore the road on the right), following the rocky slopes of Monte Cetona to reach Fonte Vetriana, where, after the medieval village, you can see the old dwellings (used to house cattle to date). Carry on downhill for 1.2 km along the main track as far as SS 478 (Sarteano-Radicofani). Turn right towards Sarteano (7 km).