urban center vs Pergamon

urban center and Pergamon both are nouns.

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

urban center (noun)	Pergamon (noun)
a large and densely populated urban area; may include several independent administrative districts	an ancient Greek city located in the western part of what is now modern Turkey; the technique of preparing sheepskins as parchment was developed here