Today is the Feast of Our Lord Jesus Christ, King of the Universe, celebrating the final victory of Christ over sin and death, when His Kingdom will reign for all time. It is also the final Sunday of the Church year. Next Sunday is the First Sunday of Advent, which begins the new Church year, and the season of Advent.
C.S. Lewis describes the Incarnation, when Christ entered into this world, as a sneak attack by God to recapture our captured planet, and to restore the Kingdom of God. The Kingdom of God exists wherever and whenever God is King. Heaven, which has always operated under the authority of God, is the Kingdom of Heaven. Our planet Earth was the Kingdom of God, until sin entered into our world through the rebellion of our first parents, Adam and Eve. This was the great Fall in which we welcomed, not God, but the Evil One, to rule our world. And we human beings became slaves to Satan.