La Cova Fumada is a no-frills fish bar in Barceloneta that claims — with solid evidence — to have invented the bomba, the fried mashed potato ball stuffed with meat that became one of Barcelona's signature snacks. The bar has been in the same family since 1944 and shows it: cash only, no sign outside, no reservations, tables that fill by 10am.
The rest of the menu runs to grilled fish, sardines, and whatever is fresh that day. Come for breakfast or early lunch; the kitchen shuts at 3pm and the bomba runs out faster. One of those places that is exactly as good as its reputation.