Always cramped, but very quick
If you want to give yourself a “baño de humanidad” (bath of humanity), go to Los Diamantes bar (Diamond Bar) and have yourself a caña and some tapas. A tiny place, but always packed with people.
Los Diamantes bar is situated at the beginning of Calle Navas, one of the most popular streets because of its Tapas Route (Ruta del Tapeo). It is pedestrian and always packed with young people at cocktail hour and before going out at night.
The place is always packed, but there is an advantage: The service is quick, and the fact that it is cramped is more than an inconvenience actually quite amusing.