From Florence and Siena:

Exit the autostrada at Firenze Certosa and head in the direction Siena/Grosseto. When you arrive at Siena, continue along highway SS223 towards Grosseto. Approximately 35km after Siena, you will pass over a long bridge followed by a long straight tunnel. Immediately after leaving the tunnel, exit the highway to the right at the exit marked Casal di Pari. Turn right at the T-junction and follow the signs for Grosseto and Il Passo degli Ulivi. Continue along this road for another 6km until you find the turn off for the agriturismo on your right.

From Rome:

Head in the direction of Civitavecchia/Grosseto. When you reach Grosseto, take highway SS223 towards Siena. After around 25km you will find the exit for Paganico and Monte Amiata on your right. Exit the highway, drive through the town of Paganico and continue towards Monte Amiata. 2km after Paganico turn left towards Monte Antico and pass under the arch of the railway bridge. Follow this road towards Petriolo/Siena for approximately 3km until you find the sign on the left that indicates the turn off for Il Passo degli Ulivi.