From North:

Speedway A1 to Florence, then take Impruneta exit. Continue on the way to Siena then take Siena-North exit. Follow the signs to Castellina in Chianti.
 

From South
:

Speedway A1 from Rome to Val di Chiana, then take Valdichiana exit. Continue on the Bettolle-Siena way then follow the signs to Florence. Take the Siena-North exit and follow the signs to Castellina in Chianti.

GPS coordinates:

Latitude: N. 43° 23' 56"
Longitude: E. 11° 18' 24"