Sweet buffalo mozzarella is paired with grilled zucchini. (Michael S. Wirtz / Inquirer)

There is a full moon hovering over the I-95 overpass tonight. But from my seat inside Radicchio, the glowing orb beaming through a corner of the windowpane looks like just another high-tech light fixture illuminating the crowd.

It's after 8 on a Tuesday night, but customers are still surging into this cozy but isolated sliver of the city. The locals in this charming enclave of 19th-century brick rowhouses on the fringe of Old City - an urban valley bordered by the Ben Franklin Bridge to the south and the interstate's elevated on-ramps to the north - had this corner trattoria to themselves for what seemed like a blip in time after it opened in May. But the food was too good and too fairly priced to remain a secret.

Grilled whole Dover sole expertly filleted tableside for $20? Warm slices of sweet buffalo mozzarella nestled alongside grilled zucchini? Pounded veal chops topped with lemony arugula salad? Just try to keep it quiet.

So these days, this small, peach-colored room seems divided between two camps: tables full of beautiful, leather-clad Italians seeking out an authentic taste of home, and another group that owner Luigi Basile calls "the Moore Brothers crowd." These are the monied wine aficionados from Society Hill and Rittenhouse Square who gleefully flock to local BYOBs with contraband bottles from New Jersey (home of the climate-controlled Moore Brothers wine boutique in Pennsauken) that often cost more than their meals.

I'd say the Italians are better equipped than the largely silver-haired wine crowd to deal with the din in this spare, modern room. A natural affinity for speaking with their hands and a propensity to sit within kissing distance gives them a fighting chance to communicate amid the deafening noise.

But don't speak. Just eat. Because, while Radicchio is far from perfect, it's one of the best in a wave of affordable trattorias to open in Philadelphia this year.

Basile, who also owns Laceno Italian Grill in Voorhees, grew up in a small town near Naples. With Mexican-born chef Pascuale Trinita, he has created a concise menu with distinctly authentic flavors that come from simple ingredients, good golden olive oil from Puglia, and a steady-handed touch.

One taste of the complimentary bruschetta - crisp little toasts mounded with lusciously ripe, basil-laced tomatoes - and it's clear where the meal is heading. As I bite into the rigatoni amatriciana, it is so perfectly al dente that my teeth suddenly slow halfway through before they snap the pasta tubes. It's like a textural drum roll that makes way for the taste of the sweet onion and porky pancetta cradled inside.

Whole fish is clearly Radicchio's calling card. And it's worth ordering just to see the harried, quick-talking young servers suddenly stop for a moment to elegantly strip a sole of its browned fillets, swish the pan, and drizzle the plate with spoonfuls of balsamic-infused oil. The fish itself is delicious and, at $20, a bargain considering that most restaurants would charge anywhere from $28 to $42 for it.

But Radicchio should be just as well known among cheese lovers for its mastery of mozzarella. Thick wedges of buffalo mozzarella, flashed in the oven and served with roasted vegetables, were so sweet that each warm mouthful was like an ambrosial milk pudding.

The fresh cow's milk mozzarella, from Claudio's in the Italian Market, was a perfect counterpoint to silky sheets of prosciutto, both in a simple lunch salad and in a more elaborate bruschetta, an awkward but devourable napoleon tiered with sliced tomatoes over toast.

But undoubtedly the best cheese appetizer was the scamorza al Radicchio, smoked mozzarella briefly grilled and then splashed with balsamic and white wine. It had tang and verve, with the smokiness cut by bitter shredded radicchio.

There were other starters of note that evoked the satisfaction of rustic flavors. A simple salad called campo di fiori brought a delightful combination of green beans, radish and green olives, each with its own distinctively flavored crunch. Succulent grilled shrimp arrived on a bed of creamy white beans with snappy asparagus segments cradled in a radicchio cup.

Steamed mussels and little clams came in a standard white wine sauce but were buttery rich, their seafood flavor heightened and full rather than brackish.

Given such promising beginnings, I couldn't help feeling a twinge of disappointment at some of the entrees. Several were overcooked: the roasted Cornish hen, the veal saltimbocca overwhelmed by its prosciutto "lid," the chewy lemon chicken, and the dry grilled jumbo shrimp.

Too many of the pastas used a creamy tomato blush sauce as a crutch, dulling each one into monotone richness. And an otherwise intriguing risotto made with smoked mozzarella and sausage had the telltale liquidy gravy of a cheater's pilaf made ahead and finished to order. (A good risotto should swell and swoon across the plate, but never run.)

The main courses weren't all frustration, though. I had a chicken paillard at lunch that was sublimely moist, the thinly pounded sheet of white meat flashed on the grill and topped with an arugula salad ribboned with artichokes and roasted sweet peppers.

A similarly inspired dinner entree brought the veal variation, a flattened Milanese chop pan-fried and then mounded with a salad of arugula and tomatoes. In both cases, a bright dressing of lemon and great olive oil made the plates sing.

Thin veal medallions in a light, lemony brown sauce had the tender delicacy the lemon chicken lacked. And a satisfyingly rustic lamb chop special was served with porcini mushrooms sauteed in demiglace.

The blush sauce seemed just right for the superb homemade gnocchi lightened with ricotta, which were irresistible. But my favorite pastas came topped with lighter, clear sauces.

The best was a fusilli special, made with an excellent fresh pasta from Westmont's Severino that looked more like a narrow noodle twisted into a straw than the usual store-bought spirals. It was served with the same bounty of beautifully sauteed seafood that came with the linguine del mare - tender sauteed shrimp and thin coins of perfectly browned scallops. But pepper flakes added to the garlicky wine sauce gave a lively flicker of heat to the juice trapped inside each noodle.

Radicchio drops the bocce ball with brought-in desserts of varying quality. The tri-colored pumpkin cheesecake was a surprising success, but the tiramisu was dry and the key lime pie was a curious shamrock green.

But when you order right, so much impresses at this corner cafe. Especially if you happen to be sitting with (a) a great bottle of wine, or (b) one of those beautiful, leather-clad Italians.