Windy City vs urban center

Windy City and urban center both are nouns.

Word	Noun	Adjective	Verb	Adverb
Windy City	Yes	No	No	No
urban center	Yes	No	No	No

Windy City (noun)	urban center (noun)
largest city in Illinois; a bustling Great Lakes port that extends 26 miles along the southwestern shoreline of Lake Michigan	a large and densely populated urban area; may include several independent administrative districts