urban center vs Philadelphia

urban center and Philadelphia both are nouns.

Word	Noun	Adjective	Verb	Adverb
urban center	Yes	No	No	No
Philadelphia	Yes	No	No	No

urban center (noun)	Philadelphia (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