coming to Chicago
While Spiaggia is certainly the pinnacle of Chicago's Italian fine dining, it wouldn't be my first recommendation for true, old-fashioned Italian. Its menu items run more towards the refined (e.g. wood-roasted filet of turbot with sunchoke puree, trumpet royale mushrooms and mushroom veal reduction, etc.) than the classic, and its clientele will likely be in fine evening-wear. Don't get me wrong -- Spiaggia's offerings are exquisite, but it will be a different feel (and price tag -- $165 for the tasting menu, pre-wine and -tip) than some of our other Italian haunts.
My top recommendation for old-fashioned Italian is La Scarola, in West Town (www.lascarola.com). Welcoming service, generous portions, a cozy storefront, and classic renditions of all the dishes you'd expect (linguine and clams, eggplant parmagiano, and the best calamari I've ever had).
Of course, there are many casual fine-dining Italian restaurants (Coco Pazzo, Cafe Spiaggia, etc.) on the spectrum between La Scarola and Spiaggia, but if you want authentic, delicious, and filling, I'd go with La Scarola.