From Rome:
You can get A12 tollroad up to the end, then continue on via Aurelia.
At Km 139, go to Orbetello - Porto Santo Stefano.
After Orbetello, get the way to Porto Santo Stefano. From Porto Santo Stefano get the "Campone" (Cemetery) road for some 12 Km (7 Miles).
Here you should find a cross with 2 roads on the left, and a brown wood fence on the right. You arrived.

From Florence:
Get the road Florence-Siena, then the road Siena-Grosseto. From Grosseto get the via Aurelia up to Albinia, where you'll find the road to Porto Santo Stefano.
Once in Porto Santo Stefano, get the "Campone" (Cemetery) road for some 12 Km (7 Miles).
Here you should find a cross with 2 roads on the left, and a brown wood fence on the right. You have arrived.