urban center vs Timbuktu

urban center and Timbuktu both are nouns.

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

urban center (noun)	Timbuktu (noun)
a large and densely populated urban area; may include several independent administrative districts	a city in central Mali near the Niger river; formerly famous for its gold trade