Dictionary.com/empyrean:

empyrean (em-pie-REE-un; -PEER-ee-) noun

1. 1. The highest reaches of heaven, believed by the ancients to be a realm of pure fire or light.
   2. The abode of God and the angels; paradise.
2. The sky.

[From Medieval Latin empyreum, from empyreus, empyreal. See empyreal.]