The street level is an art gallery featuring the work of up-and-coming painters, sculptors, and photographers, but the lower level is one of San Sebastián's best jazz venues. With its stone walls and funky alternative vibe, this place has been hosting jazz and blues performers Tuesdays through Thursdays for over 20 years. It consistently draws a crowd of über-cool jazz aficionados in their 30s and older.

Closed Mondays.

There's a variety of pintxos at this wonderful little Casco Viejo bar, but the real reason to come is to sample the ones made with anchovies. You may think you don't like this small fish, but the fresh ones here, topped with spider crab cream, sea urchin roe, or jardinera (finely diced peppers in a sharp vinaigrette), are guaranteed to change your mind. A steady stream of locals and tourists file in and out of the small square bar (whose only real stab at decor is the anchovy pintxos menu printed on a large fish-shaped piece of cardboard behind the bar) to nosh and toss back txakoli.

Locals describe Bataplán as "de toda la vida"—a classic that's been around their whole lives—and the younger ones, at least, are right. Opened in 1979, the disco owes its longevity to its great location right on La Concha beach; it draws a diverse crowd, including celebrities like Antonio Banderas and Charlize Theron in town for the annual film festival. The interiors are mod (including one seating area with pods that look like they're straight out of a sci-fi movie), and the music ranges from hip-hop and house to soul.

Closed Monday through Wednesday.

The almost rococo display of pintxos at this bar can be overwhelming—but luckily, you can pretty much close your eyes and point; every dish here is a winner. Our favorites: foie gras with peeled grapes, and txalupa, a puff pastry filled with mushrooms and langoustine in a cava wine reduction (order a glass of cava to go along with it). The bar's location in the residential neighborhood of Gros means that it draws a nicely mixed crowd, including families.

A cozy sliver of a bar, with a faintly nautical decor and a sound system piping in rock hits from the '70s and '80s, Corto Maltés packs in a diverse crowd (twenty- and thirtysomethings on the weekends, and the over-40 set on weeknights). The real reason to go is for the Champagne and excellent cocktails prepared by the friendly staff. The mixed-drink choices aren't especially inventive—gin and tonics, cuba libres, etc.—but they use high-quality spirits and freshly squeezed juices.

Harlem it ain't, but this Cotton Club is still a great place to dance. On Thursdays, Fridays, and Saturdays, a clientele of twenty- and thirtysomethings comes to groove to DJ-spun tracks. Pop, rock, and soul musicians also perform live (check the calendar on the website). Set in the neighborhood of Indautxu, southeast of the Guggenheim, the moody-looking space is decorated in black and red with dark metalwork. It's also small—only about 100 people can fit inside—so steer clear if bumping elbows on the dance floor isn't your thing. The bar serves more than 100 varieties of rum and whiskey.

Over 50 years old, this place—currently run by the fourth generation of the same family—has a cheerful bar in its front room and an informal sit-down restaurant in back. It's locally famous for its pintxos, especially the fried croquettes and the triángulos (triangles) and torres (towers): stacked finger sandwiches with alternating layers of ham, egg, or anchovies, dressed with mayo and the house's secret sauce. A glass of txakoli, the slightly effervescent local white wine, or a kalimocho (a mix of red Rioja wine and cola) makes the perfect accompaniment.

Housed in an old theater building, this place morphs from a restaurant and café frequented by students to one of Bilbao's best places to hear live bands—everything from rock and reggae to local music (check the website for the schedule). Every weekend, DJs spin the latest hits, including pop music sung in Euskara (Basque). If you've got kids, take them here for a Sunday-afternoon clown show.

Known for its massive collection of rums from all over the world, this slim, dark bar has shelves cluttered with old bottles and walls plastered with vintage posters. Locals hang out here all day—whether it's to sip a vermouth aperitif before dinner while they extract delicious periwinkles from their shells, or to sample exotic rums from places as diverse as the Caribbean, Austria, and Thailand.

Cuchara serves up the most sophisticated pintxos in town: tomatoes stuffed with ventresca (tuna belly) and bonito, crispy pig's ear with garbanzos, and creamy sweetbread croquettes. The place draws crowds of food-obsessed twenty- and thirtysomethings; it's not your aita's (father's) pintxos bar (though one bite would probably win him over). If the weather's good, come early to snag one of the four outdoor tables, order a glass of red wine from Rioja or Navarra, and watch the foot traffic in the Casco Viejo.

This cavernous, grand old bar, where pata negra hams hang above dark-wood tables and benches, has been around since 1927. It still draws crowds after all these years—mostly locals who come for the fantastic Ibérico ham, the classic Gilda pintxo (semi-spicy guindilla peppers skewered with green olives and a salted anchovy), and a tasty house red wine from the nearby Rioja region. There's a shop selling vintages and gourmet food items right next door.

Toss back a few cañas at this convivial Casco Viejo bar, which stays hopping late into the evening. There's an excellent selection of cheeses, which you can have paired with anchovies, tomatoes, or peppers (or served alone) on bread; if you're feeling bold, try the stewed cockscombs instead. The brightly lit, compact space, done up in pale woods, has a small area for sit-down meals, but it's more fun to hang out close to the bar (and the food) instead. If it's late and everyone is happily buzzed, order a glass of wine or a zurrito and toast your neighbors with the Basque word for "cheers": Osasuna!