The most desolate farm! (Full screen, please)

Sierra de La Pedriza, Spain.
I think this farm is still worked, the roof has been repaired recently - but who farms here and what they farm, is a complete mystery to me. Suggestions welcome! (I have already dismissed granite as the crop ... but really, there isn't anything else!), There were no goats, nor horses and although the next farm along the trail a couple of miles away had about 100 beehives, nothing of the sort was in evidence here.