alto relievo vs high relief

alto relievo and high relief both are nouns.

Word	Noun	Adjective	Verb	Adverb
alto relievo	Yes	No	No	No
high relief	Yes	No	No	No

As nouns, alto relievo and high relief are synonyms defined as:

alto relievo and high relief: a sculptural relief in which forms extend out from the background to at least half their depth

Other synonyms of alto relievo include alto rilievo.

alto relievo (noun)	high relief (noun)
a sculptural relief in which forms extend out from the background to at least half their depth	a sculptural relief in which forms extend out from the background to at least half their depth