Portland vs urban center

Portland and urban center both are nouns.

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

Portland (noun)	urban center (noun)
largest city in Maine in the southwestern corner of the state	a large and densely populated urban area; may include several independent administrative districts
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