Spanish capital vs capital of Spain

Spanish capital and capital of Spain both are nouns.

Word	Noun	Adjective	Verb	Adverb
Spanish capital	Yes	No	No	No
capital of Spain	Yes	No	No	No

As nouns, Spanish capital and capital of Spain are synonyms defined as:

Spanish capital and capital of Spain: the capital and largest city situated centrally in Spain; home of an outstanding art museum

Other synonyms of Spanish capital include Madrid.

Spanish capital (noun)	capital of Spain (noun)
the capital and largest city situated centrally in Spain; home of an outstanding art museum	the capital and largest city situated centrally in Spain; home of an outstanding art museum