If you hadn’t heard this word before, you will in Spain (or Europe) in
general. I don’t know many other Erasmus programs, but I would 
venture to say that the Oviedo Team is one of the most enthusiastic group of international students in Europe currently. Having 1 of the 3 ESN houses in Europe, you can see the efforts to make sure us international students have fun. Their motto that they include in every event post and informative email is in the heading. ESN Trabaja, Tú te diviertes (ESN works, You enjoy). Honestly, they are not always the most organized but I enjoy every minute of every event and trip I go on with this group.
The first week you should find the ESN flyer with a list of welcoming activities, one each day, including a city tour and the hike up to Naranco. 
Through ESN Ihave met hundreds of people all over the world. It’s incredible. Not too mention, the perks of discounts and not having to plan a trip as they do so many for you with groups of 60 or more. ESN Oviedo is probably the best one in Europe (not biased at all), especially if you love to socialize and have a good time surrounded with people all over the world.
p.s. Tapas Tuesdays is a lot of fun. Pretty much an international friend networking opportunity if you ask me.
p.s.s. La Bellota has some really amazing complimentary fried shrimp if you like shrimp.