The next logical stop for you will be a restaurant. Unless you’re accompanied by someone who knows the town a little, however, I’d be very careful about where to go. Of course, since you’re in Siena, surrounded by Medieval Tuscan ambiance, everything will taste good, and nothing particularly bad will happen to you if you choose to eat any-old-where, but wouldn’t you rather avoid the possibility of ending up unsatisfied, torpid, and irritated with a uselessly inflated check to boot? Wouldn’t you rather have a good experience, leaving the restaurant well-fed and invigorated? (I hope this is a hypothetical question for you.)
I am sure that people get so tempted to eat in the sun in the main square (Il Campo) but you probably should know that it’s not the best place to go. The piazza is beautiful but it’s better to go and sit on the bricks there and have a nice ice cream, sandwich, or even a drink but the restaurants surrounding it are not exactly what you are looking for. My first thumbs down goes to ristorante La Speranza.
First of all, you’ll have to wait a long time to get your food and meanwhile you will be consuming bottles of water for 4 euros each and the water is basically tap water filtered through this little machine and because it has been working so much it no longer filters. The water in Siena is not potable since it runs through very old rusty pipes. Once your food arrives you’ve lost your appetite because the piazza gets very, very hot. So, you get your hot food added to the 30-35 degrees celsius temperature and you start perspiring like a fountain. Long story short, you’ll also have to pay a hot bill in the end and be mad for the rest of the day. This is how the restaurants in the piazza work. They don’t have regulars who go there to eat, their customers are one-time visitors who eat and leave and never come back, so profit, not food, is their top priority. The same goes for all the piazza restaurants. Another place I would skip is Gallo Nero. Besides the fact that the owner makes his profit by hiring illegal immigrants and barely paying them (only if begged enough), the food there is not even close to being good, nor does the menu ever change. The restaurant works with groups of tourists, usually old people or Japanese, who don’t really care or know much about authentic Tuscan food or just don’t realize that they’re eating recycled bad food (and not exactly "medieval" as the restaurant claims). Although it look cosy from the outside, don’t let yourself be misled by the interior of the restaurant (which, by the way, used to a slaughterhouse. Really).
By now you’re probably wondering who I am and how I know all this stuff. I’ll tell you.
I’ve worked (and eaten) in most restaurants in Siena and I know what I am talking about. If you care to have a truly good meal, go to Enoteca I Terzi in Via Dei Termini 7, where you will find a large selection of wines (the owner knows quite a bit about wine) and a few carefully chosen daily specials to go with it. Trattoria Pappei is a very nice place right behind the Palazzo Pubblico.
There’s also Osteria Le Logge in via del Porrione 33 where you can actually see your food being prepared. Ristorante Tre Cristi is by far the best place in Siena for seafood and although it’s a little pricey it’s worthy. If you’re looking for a quick fix there is a little place called Il Grattacielo in one of the little tunnels in via Banchi di Sopra where you can have a nice dish made of pickles, ham, salami, olives and of course, cheese accompanied with a nice house wine. And if you’re just looking for a tasty slice of pizza, then check out the tiny Pizzeria San Martino in via del Porrione - you won’t regret it!