Eurocoin is right. But there is a service that does "the travelling" for you. Probably only interesting if you got many different currencies,
for only a few pesetas it will be to costly i guess, because there is a charge. On the other hand travelling to spain for "a few bucks" is`t an option really.
But if you (plus friends etc.) got notes and coins of many countries like austrian Schilling, German Mark, Irish pound a.s.o.
it might be a good thing www.euromoney24.com you can exchange or donate to Unicef.
I found this like 3 month ago because my father had found some 350 german marks....nice surprise