וּדְמ֞וּת עַל־רָאשֵׁ֤י הַחַיָּה֙ רָקִ֔יעַ כְּעֵ֖ין הַקֶּ֣רַח הַנּוֹרָ֑א נָט֥וּי עַל־רָאשֵׁיהֶ֖ם מִלְמָֽעְלָה׃
And over the heads of the living creatures there was the likeness of a firmament, like the colour of the terrible ice, stretched forth over their heads above.
Read Jewish philosophical commentary on Ezekiel 1:22: and classical philosophical sources.