Dean C.
Google
Warning: I wouldn't advise people who suffer with sensory overload not to go but my advice would be to take someone along with you who is good at navigating their way through crowds. At the Mercantic you will see stalls selling handmade jewelry, fabrics and other crafts. You will also see the Bibliotheca, one of the biggest, and I mean massive, second hand bookshops in the world, as well as being a jazz venue and a place where random people can play the several pianos dotted around the place. You will also be greeted by the height of Catalan visual culture i.e. stained glass Infront of the loos depicting generously built naked young women sitting provocatively on the lavotory in art deco style. I'm sure that appeals to a certain type of person, but no one I know.