Coming from Rome: Exit from A1 at no. 29 Chiusi-Chianciano Terme.
Follow the signs for Chianciano and then for Monte Amiata. Once you're past Chianciano, you'll find Via della Foresta on the right; in less than a kilometre it becomes Via dei Poggiardelli.
Coming from Florence: Exit from A1 at no. 28 Valdichiana.
Follow the signs for Montepulciano. Upon arrival, follow the signs for Chianciano Terme. After 2 km you'll come to an intersection with signs for Monticchiello, Castelluccio, Poggiardelli; turn right and after about 2 km you'll see Via dei Poggiardelli on the left.