I've been staying near La Boqueria on La Rambla this week and the convenience has made for some wonderful meals. There are numerous 'stands' within the market as well as other small restaurants on its periphery where you can sit and eat truly wonderful, simply prepared, fresh food.
I've tried a few stands and although they have all been excellent, one in particular is my favorite del dia. Kiosko Universal is located within the marketplace near the lower La Rambla corner. Every day (except Sunday) they are open for lunch (until 4PM) and they set out dozens of ultra fresh fish including live shellfish such as razor clams, small clams and even smaller clams as well as sole, monkfish, octopus and much more. Most of the items are taken directly from the display in front of you and then cooked on the flat grill a meter or two away.
I've had their mixed seafood platter, the mixed vegetable platter, the sole with French fries (frites better than most I had in Paris) and the razor clams, all of which were outstanding.
I've also eaten at highly rated Tapas bars in the city such as Cal Pep and Taller de Tapas but there is something truly wonderful about ordering food that looks and feels so fresh that makes this experience truly wonderful for me. I imagine that almost everything comes from the suppliers at the market the same day - it certainly tastes that way.
Oh yes, most of these places also grill the local Padron peppers - they aren't very hot - they ARE delicious. All the seafood and vegetables are so good that I haven't yet gotten around to trying the meats.
I have to admit that I am unlikely to ever stay further than a few blocks from La Boqueria from now on, whenever I visit Barcelona.