Heaven vs imaginary place

Heaven and imaginary place both are nouns.

Word	Noun	Adjective	Verb	Adverb
Heaven	Yes	No	No	No
imaginary place	Yes	No	No	No

As nouns, imaginary place is a hypernym of Heaven; that is, imaginary place is a word with a broader meaning than Heaven:

Heaven: a place regarded by various beliefs as the abode of their deities; also a place where good people are believed to go after death
imaginary place: a place that exists only in imagination; a place said to exist in fictional or religious writings

Other hypernyms of Heaven include fictitious place, mythical place.

Heaven (noun)	imaginary place (noun)
a place regarded by various beliefs as the abode of their deities; also a place where good people are believed to go after death	a place that exists only in imagination; a place said to exist in fictional or religious writings