My first impression was this has to be one of the Europe's busiest living monuments. Its interesting 19th century architecture, a structure of glass and iron, creates an environment in which one knows he or she can find just about anything. Or at least wander, loiter and enjoy trying.
La Boqueria is situated halfway between Plaza Cataluyna, Barcelona's main travel hub, and its port. The massive amounts of fresh seafood are just a pronouncement of locale -- this is Spain and the Mediterranean is close. Today's catch abounds -- partake. It is also located along the pedestrian corridor, Las Ramblas, where one can witness a variety of shops, to include street performers. For tourists.
The uniqueness of La Boqueria is while most locals seem to avoid the tourist-oriented Las Ramblas, they frequent La Boqueria. This is an authentic, functional market with side and back alley entrances. Convenient, essential, fascinating.
This is another European market one should not miss. It truly is a separate world unto itself.