This is undoubtedly the tapas bar for that authentic Catalan experience. It's a Barceloneta institution, with a long, narrow, crowded bar that is incredibly popular with locals. It might not look particularly special, but edge your way to the bar, order whatever tapas takes your fancy, and wash it down with a beer or two.
C/Balbao, Barceloneta; Nearest metro: Barceloneta
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Is this your business?
The pimientos del padron are delicious, and as Spaniards said, some of them are hot and some not (unos pican y otros no).