Ah, where to start???
Barçelona must be my favourite city, after London. Fantastic place, full of stuff to see and do.
Obviously, the Gaudi stuff; La Sagrada Familia, Parc Guell, etc. The Bari Gotic, with really old stuff. Las Ramblas, although it’s a bit tourity and superficial, but you’ve got the big food market off there, that’s pretty amazing. and all the little side streets, with little bars and tapas joints.
Footie fan? Dunno if you’ll get to see a Barçelona game, but a stadium tour might be good fun.
Tibidabo, up on the hill behind the city, offers some spectacular views.
Just mooch about, enjoy what you find.
And the best bit of advice I was given?
Wear comfy shoes…