The book of the Revelation of Jesus Christ describes through visions given to the Apostle John events that have occurred and those that will occur up to the return of Jesus as King.
And I looked, and, lo, a Lamb stood on the mount Zion, and with Him an hundred forty and four thousand, having His Father’s name written in their foreheads.Revelation 14:1
Jesus is the Lamb of God. The vision shows Him standing on mount Zion. In Psalm 2 we read that God says:
Yet have I set My king upon My holy hill of Zion.Psalm 2:6