Revelation 4th Division, Footnote A
IV: The Salvation of the Church (11:19 - 15:14) or "Judgement Day as seen by Christians"
A. The Setting: The people of God are singing praises before the ark of the covenant (22:19).
Remember.. the ark was the "box" in which the stone tablets of the 10 Commandments were kept and was the symbol of God's presence in the midst of his people. It was kept in the "Holy of Holies" in Solomon's temple - a place no one could enter, except for the High Priest and then only once a year. This one day was called the Day of Atonement.
Now, the heavenly ark is visible as the curtains are opened allowing... all of God's people into the heavenly holy of holies. This is done to let the people of God in heaven know that their Day of Atonement has come, they are utterly forgiven for everything and they can see for themselves the symbol of God's presence in their midst. This is happening because the heavenly temple itself is no longer necessary: the resurrected faithful have no need for a temple and an ark because God himself is in their midst. That they see the ark is a message to them (and especially to John's readers) that God's covenant with his people has stood firm through time.
Welcome to an unusual, mystic, and powerful way to tell the Story of Christ.