urban center vs Portland

urban center and Portland both are nouns.

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

urban center (noun)	Portland (noun)
a large and densely populated urban area; may include several independent administrative districts	largest city in Maine in the southwestern corner of the state
	freshwater port and largest city in Oregon; located in northwestern Oregon on the Willamette River which divides the city into east and west sections; renowned for its beautiful natural setting among the mountains