6 And God said, “Let there be a vault between the waters to separate water from water.” 7 So God made the vault and separated the water under the vault from the water above it. And it was so. 8 God called the vault “sky.” And there was evening, and there was morning—the second day.
What did God create on the second day?
On this second day, God separated the water on the ground from the water above the sky. The sky (space), as we can see above, separates water above and water below.

How many Heavens do we have according to the Bible?
According to the Bible, we have three heavens. The first heaven appears in Genesis 1:6-7, a dome “sky” that separates the waters below from water above.
The second heaven appears is not scripturally written as second heaven, but the scripture talked about third heaven in Hebrew 7: 26 and 2corinth 12:2; this implies there is second heaven.
To further explain where second heaven exists, look at Genesis 1: 14-17, referring to Sun, moon, and stars as heavenly or celestial bodies. Remember in Genesis 1: 1, God created the heavens/universe, including the Star, Sun, moon, etc.
If this category of heavenly bodies is not located in our sky (first heaven), or domain of almighty God (third heaven, then it’s the second heaven.
Who lives in second heaven?
The second heaven is the campground of the fallen angels, principalities, and rulers of darkness. It’s is where devils rules and perpetuate all his evil devices, misleading and destroying lives.