Evenings in a foreign city can be boring unless you've planned your nightlife outings carefully... Going to the movies can be a great way to disconnect from so much sighseeing, give your brain a rest from so much foreign language babling and... mingle with locals at the same time! Isn't that a cool thing?
When I travel, I always try to go to the movies one evening. It's a cool experience!
In Barcelona, I recommend Yelmo Multicines, located near the beach of the Olympic Village because it's easy to reach by subway, there is a lot of nice restaurants in the area and... it programs mainstream movies in English.