While speaking of the sin of bragging, Paul writes about “someone” that enjoyed a most incredible experience…
I knew a man in Christ above fourteen years ago, (whether in the body, I cannot tell; or whether out of the body, I cannot tell: God knoweth;) such an one caught up to the third heaven. And I knew such a man, (whether in the body, or out of the body, I cannot tell: God knoweth;). How that he was caught up into paradise, and heard unspeakable words, which it is not lawful for a man to utter.
2 Corinthians 12:2-4
Now the latter context makes it obvious that Paul is speaking of himself. The most likely explanation is that Paul took a journey to the throne of God. In the above text, he uses the expression “third Heaven” which is a figure of speech Jews used to describe the home of God (the first “heaven” is the sky where the birds fly; the second “heaven” is space, the final frontier). A likely timeline for this event would be the occasion when he was stoned and left for dead (Acts 14:19). As Paul says, even he was unaware whether he was killed or simply unconscious and permitted to see what he saw in a vision.
Either way, Paul took a journey to the Paradise of God and returned with visual evidence that everything he was fighting and suffering for was real. He didn’t need to see Heaven to know it was real, however: He already knew on account of seeing the resurrected Christ, and by the many miracles he did. Still, the sight of it had to be quite fulfilling.
A lot of people wish they could just “see” this or that, so they’d “know” their faith is real. They are like Thomas, who sought visual evidence in the form of Jesus’ nail-driven hands and feet. But Jesus’ words to Thomas apply to us who are faithful centuries later:
Jesus saith unto him, Thomas, because thou hast seen me, thou hast believed: blessed are they that have not seen, and yet have believed.
I don’t need to touch Jesus’ hands to know they were nailed for me. I don’t need to see Heaven to know it is waiting for me. Did 15th Century Europeans need to see the new world or did they trust the word of explorers that it was there? Trust is all the evidence I need. Faith is the evidence of that which I haven’t [yet] seen (Hebrews 11:1).