Tour Italy in a saddle
True story: First time I ever fell off a horse was in Tuscany—riding through the Mugello hills northeast of Florence.
I don't mention this to discourage you, but because falling off that horse is only the second thing I think of when I think about riding in Europe.
The first thing I think about is the awesome morning I once spent on horseback riding across the hills of Sicily with a local who told me tales of life in central Sicily and pointed out caves where mafiosi used to hide in the bad old days. » more
But those were just day rides—a chance to get off the tourist mill and get in the saddle for a few hours.
If, however, you'd like to actually ride across the countryside on a multi-day horseback tour of Italy there are plenty of resources in the "Links" section: