urban center vs Bremen

urban center and Bremen both are nouns.

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

urban center (noun)	Bremen (noun)
a large and densely populated urban area; may include several independent administrative districts	a city of northwestern Germany linked by the Weser River to the port of Bremerhaven and the North Sea; in the Middle Ages it was a leading member of the Hanseatic League