Board Thread:General Mod Discussion/@comment-46.233.112.99-20161220220903/@comment-25101089-20161222135615

Since Cuiviénen was a bay of the Sea of Helcar, it would be gone once the Sea was drained. As for Hildórien, there is no source, only my own speculation and what I feel would be most fitting. Cuiviénen and Hildórien, as places of awakening, are almost mythological, and I think that to place them in the world as regions one might visit would take away from that.

It reminds me of how nobody has managed to identify a region in the real world corresponding to the biblical description of the Garden of Eden. In Morgoth's Ring there is a tale of the 'Fall of Man' where Morgoth or Sauron comes to corrupt the first Men and they suffer punishment from Ilúvatar as a result. This tale being an analogue of the Judeo-Christian Fall of Man, just as Adam and Eve were cast out of Eden and never permitted to return, it seems fitting that in Tolkien's Judeo-Christian-inspired legendarium, Men could never return to Hildórien.