Rostov na Donu vs city

Rostov na Donu and city both are nouns.

Word	Noun	Adjective	Verb	Adverb
Rostov na Donu	Yes	No	No	No
city	Yes	No	No	No

Rostov na Donu (noun)	city (noun)
a seaport on the Don River near the Sea of Azov in the European part of Russia	people living in a large densely populated municipality
	a large and densely populated urban area; may include several independent administrative districts
	an incorporated administrative district established by state charter