urban center vs Rostov-on-Don

urban center and Rostov-on-Don both are nouns.

Word	Noun	Adjective	Verb	Adverb
urban center	Yes	No	No	No
Rostov-on-Don	Yes	No	No	No

urban center (noun)	Rostov-on-Don (noun)
a large and densely populated urban area; may include several independent administrative districts	a seaport on the Don River near the Sea of Azov in the European part of Russia