Hi FamilyTraveler
Without knowing his interests it's a bit of a shot in the dark, however, for day escapade to nearby destinations, at the very least I would suggest the following:
SOME IDEAS FOR AN EXCURSION OUT OF THE CITY (by train and/or bus): BESALÚ | GIRONA | FIGUERES | SITGES | MONTSERRAT | TARRAGONA | VIC | ROSES | TOSSA DE MAR. There are literally dozens more, but that'd depend on whether he's rather urbanite or nature lover, whether he's into art, nature, history or else, etc.
Or perhaps attending an event or "festa major" somewhere in the region can be another great option to immerse yourself in Catalan culture.
If you prefer more traditional text-based advice:
http://catalunya.com/ -Catalonia’s Tourism Agency | http://www.barcelonaturisme.com/ -Barcelona’s Tourism Agency | http://en.costabrava.org/ -Costa Brava Tourism Agency | http://www.baixemporda-costabrava.org/en/ | http://www.lleidatur.com/ -Lleida and Pyrenees-Aran Tourism Agency | http://www.visitpirineus.com/ -Pyrenees-Aran Tourism Agency | http://www.turismeamposta.cat/en -Terres de l’Ebre Tourism Agency | http://www.bcn.cat/ -Barcelona City Council | http://www.girona.cat/turisme/eng/index.php -Girona City Council | http://www.tarragonaturisme.cat/ -Tarragona City Council
Whatever he does by plane will most probably require an overnight, otherwise, he'd be spending too long to/from the airports, waiting in lounges, etc. to be done in the same day (albeit I've often flown for a day-meeting elsewhere in Europe with not much problem). By plane he literally has the whole of Europe at a short flight away --Helsinki for example, which is, so to speak, in the opposite corner of Europe in relation to us, it's barely 3h away. Still, I wouldn't get carried away, while there are plenty of low-cost flights to many destinations (Barcelona is an important hub in that sense), spending many weekends abroad easily sums up and it can be quite costly. You'll probably won't like to hear this, but Eivissa (a.k.a. Ibiza) is just an hour away by plane. Florida's spring breaks pale next to the famous world-renowned Eivissa's (pronounced "ee-bee-sah") :)))
Important: without entering into politics, know he'll be staying in Catalonia, and while it's administratively part of Spain, it's not "Spain" -at least not what you might think of as Spain. It has its own language, its own culture, traditions, etc... and relationships with Spain are not precisely at their high. So it's useful to get acquainted with this fact and also to be tactful if entering into political debates or anything related to the Catalonia - Spain sphere for that matter.
If he does speak Spanish, there's no problem whatsoever speaking it to us Catalan speakers, and knowing he doesn't speak Catalan most people will oblige and respond in Spanish (or English!). Still, a few sentences here and there in our language will certainly warm up many people: https://wikitravel.org/en/Catalan_phrasebook
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