Full Idea
Plato claims that the Forms are not beyond the heavens, because they are not anywhere.
Gist of Idea
Plato's Forms are said to have no location in space
Source
report of Plato (The Republic [c.371 BCE]) by Aristotle - Physics 203a09
Book Reference
Aristotle: 'Physics', ed/tr. Waterfield,Robin [OUP 1996], p.63
A Reaction
This is an important corrective to caricature accounts of Plato's Forms (encouraged, I'm afraid, by 'Phaedrus'), when critics talk about 'Platonic Heaven'. Forms are not part of space-time. I like the view that they are hypothetical truths.