I've been inspired to publish this amateur tour d'horizon filmed just south of the hilltop town of Montalcino by this Do we need crus in Montalcino? thread in our Members' forum.
I think the variability in terrain even so close to many of the finest slopes suggests that the Montalcino zone is far too large and far too heterogeneous. But just think how many millions of hours of discussion and lobbying it would take to come up with a more precise mapping...