national capital vs capital of Iceland

national capital and capital of Iceland both are nouns.

Word	Noun	Adjective	Verb	Adverb
national capital	Yes	No	No	No
capital of Iceland	Yes	No	No	No

national capital (noun)	capital of Iceland (noun)
the capital city of a nation	the capital and chief port of Iceland on the southwestern coast of Iceland; buildings are heated by natural hot water