Santo Stefano is a beautiful vineyard in Tuscany. We rented a little Renault convertible and took a day trip from Florence (Firenze) to Siena.
I learned three things that day:
1) Siena is amazing and I need to go back to experience the Palio di Siena (if anybody out there can hook me up, please let me know!)
2) Vineyards in Tuscany don't have giant "VINEYARD" signs out front — at least they didn't back when we went. Instead, they have a hand-painted sign of a rooster. So, if you are driving through Tuscany looking for a nice vineyard to visit, go to the places advertising roosters and you'll be good to go. Wait for a "Vineyard" sign and you might miss all the good stuff!
3) Regular people aren't allowed to drive on a lot of the streets in the historic district (pretty much all) of Florence. You can get in but you're going to have a hard time getting out as you back your car hundreds of feet down alleys lined with Vespas and motorcycles. Don't ask how I know.