I thought they hinted that Elpis was in a small pocket dimension. Amaurot is definitely somewhere down in the sea off the western coast of Vylbrand. If Elpis wasn't put into its own pocket then I'd guess it'd be something like Azys La where it's fairly high in the sky. Not sure how they'd allow for any winged not ready to be released creations to be studied if they could easily fly away to the rest of the world.