guys you do need to carry id in Spain at all times even if your here on holiday and that should be your passport.
The specific law is Article 4 of Organic Law 4/2000 which states in unambiguous terms that foreign nationals in Spain must carry identity documents issued by the country of citizenship.
There are other ways around it though, get your passport copied and made smaller then carry that.
I have more in this and loads of info on Spain on my info page here
and in my new books out on Amazon and Kindle. see here

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