Over-heaven

“The names of all the stars, and of all living things, and the whole history of Middle-earth and Over-heaven and of the Sundering Seas.”
Pippin’s request of Gandalf The Two Towers III 7, The Palantir

In Elvish cosmology, Over-heaven was the highest of several levels of ‘airs’, the domain of the stars far above Arda. Beneath them the Sun and Moon travelled through the sky. This highest level of the heavens was known to the Elves as Ilmen (and also by the poetic name Tarmenel).