Although Barcelona has a wide range of tapas bars and restaurants throughout the city, the downtown area is home to some of the most renowned 'small plate' establishments. Due to the eclectic vibe of 'Ciutat Vella' (Old City), most tapas bars are informal, small and always bustling. Whether you're looking for greasy or gastro tapas, there are some truly excellent places to check out.
Barcelona's downtown core is fairly spread out amongst the various neighborhoods. Between the Raval, Gothic Quarter, Born and Barceloneta, you'll never run out of options. If you're a foodie and want to sample Ferran Adria style cuisine (on a much different scale), then try gastro tapas at some of the restaurants where they serve typical Spanish and Catalan dishes with an elegant, Mediterranean twist. Some new Gastro tapas places include Elsa y Fred and the Restaurant Ohla (in the hotel).
If you'd rather experience 'under the counter' tapas - meaning greasy and often scary looking, but absolutely delicious -then El Xampanyeria is one of the best places. It's not only for the free tapas (if you buy a drink), but this place embodies the genuine Barcelona tapas experience and is the perfect way to get a feel for the REAL local tapas scene in the city.