There are plenty of hostels in Spain, mostly in Madrid. Prices can vary from €15 to €25 per night.
Xanascatwww.xanascat.cat is the National Network of Youth Hostels of Catalonia if you are visiting Barcelona, Girona, Taragona or other locations in the region.
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Spain: Hotels and Accommodation: Hostels is based on work by Denis Yurkin, andres, Eco84, Stefan Ertmann, D. Guillaime, Fegatur, Roundtheworld, Burmesedays, Herga, iGuide, and others. Spain Travel Guide & Spain Interactive Map is available under Creative Commons Attribution-ShareAlike 1.0. See background image credits.