Harley Street vs British capital

Harley Street and British capital both are nouns.

Word	Noun	Adjective	Verb	Adverb
Harley Street	Yes	No	No	No
British capital	Yes	No	No	No

Harley Street (noun)	British capital (noun)
a street in central London where the consulting rooms of many physicians and surgeons are located	the capital and largest city of England; located on the Thames in southeastern England; financial and industrial and cultural center