The main religion of Spain is Catholicism.Well, the main religion in Spain is Catholicism. 94% of the population is Catholic, but they do have other religions there too.
Spain is 94% Roman Catholic. All the other religions only total 6%.    
3
Muslims, Christians (who were all Catholics at this point) and Jews, in order of population numbers.
Hindu, Islam, and i think Jainism
christianity (catholics ), judaism and islam
Madrid, Barcelona, Valencia
Spain.
70% of Spain is Roman Catholic, 2% other religions,25% no religion. Roman Catholocism is a denomination of Christianity
Just like every major city you'll find all religions represented however Spain (and Barcelona) are very Roman Catholic and this is the main faith practised in Barcelona.
There are 3 major religions in Jerusalem : Judaism, Christianity, and Islam.