urban center vs City of Brotherly Love

urban center and City of Brotherly Love both are nouns.

Word	Noun	Adjective	Verb	Adverb
urban center	Yes	No	No	No
City of Brotherly Love	Yes	No	No	No

urban center (noun)	City of Brotherly Love (noun)
a large and densely populated urban area; may include several independent administrative districts	the largest city in Pennsylvania; located in the southeastern part of the state on the Delaware river; site of Independence Hall where the Declaration of Independence and the Constitution were signed; site of the University of Pennsylvania