What are the Heavenly Realms?

Engaging God in heaven is not new for Christians. For example, the writer of Hebrews said this:

“No, you have come to Mount Zion, to the city of the living God, the heavenly Jerusalem, and to countless thousands of angels in a joyful gathering. You have come to the assembly of God’s firstborn children, whose names are written in heaven. You have come to God himself, who is the judge over all things. You have come to the spirits of the righteous ones in heaven who have now been made perfect. You have come to Jesus, the one who mediates the new covenant between God and people, and to the sprinkled blood, which speaks of forgiveness instead of crying out for vengeance like the blood of Abel.” (Hebrews 12: 22-24 NLT)