"After this I looked, and there before me was a door standing open in heaven. And the voice I had first heard speaking to me like a trumpet said, 'Come up here, and I will show you what must take place after this.'" (Revelation 4.1)✞
John of Patmos described a vision of a door and a way into the Heavenly Court where God sat on his throne surrounded by the multitudes of angels and the righteous dead in Paradise all worshipping. The belief in ancient times was that Heaven was a vast solid vault set like a roof on a square flat earth entered by way of actual doors in the vault.
Jesus at his ascension is described as rising into the clouds and disappearing from view. Acts 1.9-11 described that moment, "After he [Jesus] said this, he was taken up before their very eyes, and a cloud hid him from their sight. They were looking intently up into the sky as he was going, when suddenly two men dressed in white stood beside them. 'Men of Galilee,' they said, 'why do you stand here looking into the sky? This same Jesus, who has been taken from you into heaven, will come back in the same way you have seen him go into heaven.'"✞
The idea of heaven open door reminds us also of Jesus speaking to the disciples of himself in John 10.7 when he said, "Very truly I tell you, I am the gate for the sheep." Again in Luke 11.9-10, Jesus said, "So I say to you: 'Ask and it will be given to you; seek and you will find; knock and the door will be opened to you. For everyone who asks receives; the one who seeks finds; and to the one who knocks, the door will be opened.'" Jesus told us to keep on knocking and the door into God's presence will always be opened. He or she who knocks on Heaven door are assured of entry.✞
John of Patmos then heard what sounded like a trumpet blast at the voice of Christ and was invited into Heaven by the angel who said, "Come up here." This reminded us of God's call to the prophet Ezekiel whose name literally meant "may God strengthen him" or "god will strengthen" who was similarly called up in a vision into Heaven and also described the throne of God.✞
Four times in the Book of Revelation, John of Patmos said he was "in the Spirit." The Holy Spirit took over John and gave him a vision, and showed him situations and events he could not have seen with mere human eyes. This pointed up the truth that all true prophecy comes from God through the Holy Spirit. Heaven open door invited John to come up and to come in. John described seeing the magnificent throne room of God through the door standing open.He was then invited to, "Come up here."✞