Elegant new Italian restaurants line K Street, overflow to L Street, spread to the suburbs. But the first of the northern Italian restaurants, Cantina d'Italia, continues to hold its own. It may not be as beautiful as its younger rivals, being a basement warren hung with plasticgrape vinesand studded with plaster statues, but its food is as exciting as any of them. The menu is just short of garish, and nearly everything is called a specialty. But then, the dishes usually taste like specialties. The food is not only fresh, but includes the best of the season - rugola in the salad or fresh basil in the pesto. Stiped bass might be served hot with lemon and mushrooms or cold with a thick, homemade Piemontese mayonnaise. Sometimes the pasta has been known to miss, with the sauce too thin or the noodles lukewarm; but usually the homemade noodles steam in their thick parmesan-cream-butter coating or an unctuous lobster and tomato puree with cream. The gnocchi are light and buttery, the veal beautifully cooked. And they serve kidneys several ways, or duck with olives and mushrooms in a wine-cream sauce. The choices are intriguing and ever-changing. Ingredients and their preparations are of high caliber. And nobody in town makes better cannole. The wine list is appropriately and exclusively Italian. As for the service - well, try not to hit a crowded time, or dine with somebody you want to get to know well.