Denver vs Mile-High City

Denver and Mile-High City both are nouns.

Word	Noun	Adjective	Verb	Adverb
Denver	Yes	No	No	No
Mile-High City	Yes	No	No	No

As nouns, Denver and Mile-High City are synonyms defined as:

Denver and Mile-High City: the state capital and largest city of Colorado; located in central Colorado on the South Platte river

Other synonyms of Denver include capital of Colorado.

Denver (noun)	Mile-High City (noun)
the state capital and largest city of Colorado; located in central Colorado on the South Platte river	the state capital and largest city of Colorado; located in central Colorado on the South Platte river