Aerie

From Tolkien Gateway

Aerie was an almost certainly mythical Elven realm probably invented by Bilbo Baggins for his poem Errantry where Aerie's Elven-knights dared a mariner.[1] The name is obviously fictional, made to resemble an Elvish one.[2]

References

Legendary Locations in Arda
Islands:  Meneltarma
Mountains:  Astulat · Mountains of the Moon · Merlock Mountains
 Regions:  Aerie · Belmarie · Fantasie · Last Desert · Sindanórie · Thellamie · Tode
Rivers:  Derrilyn
Other:  Caves of the Forgotten · Gorbelgod