There are few things sadder than an unloved lunch buffet whose steam table cargo goes stale from a lack of attention. It’s easy to get snobby about those wrong kind of buffets. Of that I have been guilty.

There is little happier, though, than a lunch buffet thrumming at full tilt in all its glory. This was especially true at Thanal Indian Tavern one recent Friday around noon, when the double-decker extravaganza was being constantly refreshed with fragrant mounds of spicy chili chicken, hot goat curry, pepper-flecked uttapam pancakes, and crispy rounds of medu vada fritters that wafted the earthy scent of toasted curry leaves like a Tamilian homing signal that was obviously working. The line of customers waiting for their crack at this wholesome, all-you-can-eat $14.99 South Indian lunch extended out onto the sidewalk at 20th and Arch.

This may be perplexing for locals — there has not in recent memory been such a bustling restaurant at this bi-level corner bar in Logan Square (most recently another, less-popular Indian restaurant). The mention of uttapam and spice-crusted “chili chicken” might also surprise those who know there’s been precious little cooking from Southern India in Center City to date, save for a quick-serve dosa shop on Sansom Street, the somewhat underwhelming Philadelphia Chutney Co.

That happily has begun to change in a big way in the last few months as Thanal debuted, and as one of my favorites from South Jersey — Amma’s South Indian Cuisine — opened a worthy branch at 1518 Chestnut St. And it’s an unexpected reflection of some other changes in the city, where the newly opened Comcast Innovation and Technology Center has brought 4,000 relocated employees,and stirred some unexpected perks in the surrounding neighborhood. Like the new “dosa corner” section of the menu at Thanal, which opened just one block west of the new Comcast building in late October, and which serves rarities like tandoori-roasted whole pomfret, gongura curries with tart red sorrel, and bottomless pans of Hyderabadi biryani.

“One of my partners is in the tech business, and we knew Comcast was opening up,” says co-owner Hariharan Karmegam, a self-described "Tamilian” from the beet-loving city of Madurai in Tamil-Nadu. “We knew a lot of South Indians were working there, and so now every day we see them at our buffet. We take reservations for 10, 15, 25 people at a time. And now we’re going to do a little renovation to our upstairs dining room and put a conference room up there, too.”

The crush of weekday customers, who Karmegam says also come from other Market Street office buildings, have at least 14 dishes to choose from on a buffet that changes daily. Among the recent highlights were cubes of steamed idli rice cakes tossed with crushed red chilies and coconut powder; a massive pan of masala-spiced potatoes scattered with freshly fried puri bread; and a gingery stew of curried goat cubes that were gamier — but also more tender — than any lamb I’ve had in recent memory. The steaming mound of biryani on the buffet was considerably more fresh and fragrant than the variation I’d ordered à la carte at a previous dinner at Thanal, the rice moist with vivid spice and chunks of tender, bone-in chicken nestled deep below.

A vegan mince of beet root poriyal was savory with ground coriander, fenugreek, and mustard seeds. Snappy okra pods basked in the tart richness of gongural gravy. A tall stack of uttapam pancakes made from fermented rice and lentils (the same batter used for Thanal’s crepe-like dosas) was the perfect comfort food, with colorful side dips of coconut, mint, and tomato chutneys.

The signature flavors of South Indian cooking — the pungent muskiness of curry leaves, mustard seeds, tart tamarind, dosa crepes, and the use coconut milk instead of dairy cream — are part of what distinguish that cuisine from the richer flavors of Northern Indian Mughal cooking that have long defined Indian menus for American audiences. South Indian restaurants have in recent years proliferated in healthy numbers in the western suburbs of Philadelphia ,where, not coincidentally, South Asian immigrant communities have taken root thanks to jobs at several large tech companies. The arrival of these kitchens in Center City represents a quality-of-eating-life improvement in the same way the influx of Szechuan, Shanghainese, and Taiwanese flavors represented for Philadelphians a welcome awakening to the regional delights of Chinese cuisine beyond the familiar Cantonese canon.

Thanal’s à la carte menu still touches some familiar bases from Northern Indian, to be sure, with creamy korma, dal makhni, and butter chicken gravies, as well as the usual tandoori options that remain a reliable draw for the evening crowds, who come more from the surrounding neighborhood. The dinner service is also when energy picks up at the glossy black counter that rings the moody red- and blue-lit bar, where the tavern serves intriguing Indian-themed cocktails infused with everything from black pepper tincture to Kaffir lime, fennel, and turmeric. (More could be done to improve the bar’s somewhat mundane beer and wine selections.)

The tandoori chicken was a reluctant feature, the hot pink Indian equivalent of General Tso’s chicken that Karmegam, who recently moved here from Washington, initially had lobbied to avoid. His partners persuaded him otherwise. But it is likely the least exciting thing you’ll eat here.

Chefs Honest Raj and Raja Prabu cook dishes that crackle with southern spice. Like the “gunpowder” shrimp dusted with powdered mango, curry leaves, and so much chili that the vapors rising from the sizzling plate of those plump crustaceans tickled my nose. Or the long “railway peppers” whose potently fruity spice perfumed the deep-fried crusts of the chickpea gram flour batter that cloaked the Hungarian wax chilies.

The big lamb shank rogan josh is a showstopper worth sharing, provided you order its onion-rich gravy spicy enough (Karmegam suggests a 7 out of 10 on Thanal’s scale) for the restaurant’s southern take on the Kashimiri dish, with curry leaves, chilies, and cardamom, to really pop. Tender lamb chops, meanwhile, also get the southern touch of coriander powder, coconut oil, and a ginger-garlic paste marinade before they’re roasted in the tandoor and served alongside crispy pappadam wafer cones stuffed with a crunchy slaw.

Tender stewed chicken pays homage to the famous flavors of Chettinad, a rich coconut gravy that incorporates coconut milk and coconut flakes, with vivid spice box notes of cardamom, bay, and dried kalpasi flowers, which amplify the flavors of star anise. For crispier chicken alternatives, try chicken 65, the famous street food whose nuggets of boneless meat are crusted in chili spice, mustard seeds, and a light tomato glaze. A must-get vegetarian dish is the gobi Manchurian, a mound of fried cauliflower florets tossed in the sour tang of a spicy tomato sauce typical of the popular Indo-Chinese fusion style.

In Thanal’s first few months of menu experiments, the diverse regionality of South Indian cooking itself has become even more apparent. Though Thanal’s devotees come primarily from the state of Tamil-Nadu, dishes from another South Indian state, Kerala, have been sparsely ordered, despite a well-ensconced Malayali community from Kerala in Northeast Philly. I’ll miss the tender roast duck with coconut oil, black pepper, and chilies, as well the fenugreek-flaired coconut gravy of the lobster moilee once they’re taken off the menu. But there are other dishes to replace them, like the “mutton” sukka, which is actually made with boneless hunks of lamb cooked in similar fashion to the duck. And there is also now a Malabar fish curry cooked in a coconut sauce with Kerala’s uniquely tangy black tamarind.

The tandoor-roasted fresh pomfret, though, is a rare delight for lovers of whole fish. Its flesh is deeply marinated in Kashmiri red chilies with cuminy ginger-garlic paste and herbal asafoetida, then sliced into vents for easy plucking of the Tamil-Nadu classic. Another Tamil staple is the goat trotter paya, a soup anchored by a goat’s foot that I’ve yet to come across on local menus. The foot is for flavor, mostly, as well as richness that adds a sneaky depth to the deceptively thin brown broth kissed with coconut milk and filled with nothing else but tiny bits of red onion that spark to reveal the soup’s complexity when you bite them. I believe it when Karmegam says this was his mother’s cure-all remedy when he got sick, like “Tamilian penicillin.”

When I looked up from my à la carte bowl of paya soup to check back on the swarm status of that lunch buffet, I saw it was still busy, but with the crowd now hovering near the hot tub-size vat of gulab jamun fritters bobbing in syrup for dessert. And I knew Thanal had struck a rare and coveted chord. It’s a flavorful convergence of novel-to-Center City flavors and good timing, supercharged by local development and a rocking South Indian buffet of incredible value. And it has revealed a flavorful new moment for the city that’s simply been waiting to happen.

Thanal Indian Tavern

Very Good

1939 Arch St., 215-515-2511;

Philly’s awakening to the exciting diversity of regional Indian flavors continues with the arrival of another South Indian kitchen. This full-service, bi-level corner tavern in Logan Square draws huge crowds from the nearby business district for an excellent lunch buffet laden with uttapam, goat curries, and bottomless Hyderabadi biryani. The nighttime scene shifts into spice-accented cocktails and an a la carte menu that offers more refined entrees (stewed lamb shanks, gunpowder shrimp, tandoori-roast pomfret), along with a broad menu of Tamil-flavored classics.

MENU HIGHLIGHTS Indian railway peppers; chicken 65; gobi Manchurian; onion pakora; mutton sukka; chili paneer; goat trotter paya soup; idli; medu vada fritters; gunpowder shrimp; masala dosa; kerala paratha; chicken chettinad; Thanal special goat curry; coriander lamb chops; tandoori pomfret; lamb shank roganjosh; dal makhni; karahi lamb curry; Hyderabad chicken biryani; tender coconut kheer; Madras kaapi (coffee).

DRINKS Thanal has a full bar, though its dozen beers (with a welcome handful of locals) and big-label commercial wine list are somewhat limited. The Indian-themed cocktails are where this bar is having the most fun, accenting classic mixed drinks house-infused with Indian spices, from cardamom bitters and mint in the Green Revolution, to the turmeric gin Cocktail Doctor and a Madras mule spiced with green chili vodka.

WEEKEND NOISE The dining room gets busiest during the lunch buffet, but the noise level remains reasonable.

IF YOU GO Lunch Monday through Friday, 11:30 a.m.-2:30 p.m. Dinner Monday through Thursday, 5-10 p.m.; Friday and Saturday, until 11 p.m.; Sunday, until 9 p.m. Brunch Saturday (à la carte only) and Sunday (buffet will be available by mid-March), 11:30 a.m.-2:30 p.m.

Dinner entrées, $8.99-$25.99. Lunch buffet, $14.99.

All major cards.

Reservations suggested especially for lunch Wednesday through Friday.

Wheelchair accessible ground floor only.

Street parking only.