Many saints and mystics have been given the great grace of a vision of Hell. It is a grace because it brings home in a very real way the unspeakable horrors that unrepentant sin can lead us to. It should prompt us to pray unceasingly for souls in danger of ending up in Hell. These visions have been given to canonised saints and Doctors of the Church so that they may tell us something about the nature of Hell, although the CDF reminds us that visions are often shaped by the culture of those who receive them.
Teresa writes in her autobiography about a frightening vision she had of Hell and how it haunted her the rest of her life. When writing the vision down she experienced the same bone-chilling feeling as she had at the time it took place. Here is St Teresa of Avila’s vision of Hell in her own words; she is a wise and highly credible guide…
A long time after the Lord had granted me many of the favours which I have described, together with other very great ones, I was at prayer one day when suddenly, without knowing how, I found myself, as I thought, plunged right into hell. I realized that it was the Lord’s will that I should see the place which the devils had prepared for me there and which I had merited for my sins. This happened in the briefest space of time, but, even if I were to live for many years, I believe it would be impossible for me to forget it. The entrance, I thought, resembled a very long, narrow passage, like a furnace, very low, dark and closely confined; the ground seemed to be full of water which looked like filthy, evil-smelling mud, and in it were many wicked-looking reptiles. At the end there was a hollow place scooped out of a wall, like a cupboard, and it was here that I found myself in close confinement. But the sight of all this was pleasant by comparison with what I felt there. What I have said is in no way an exaggeration.
My feelings, I think, could not possibly be exaggerated, nor can anyone understand them. I felt a fire within my soul the nature of which I am utterly incapable of describing. My bodily sufferings were so intolerable that, though in my life I have endured the severest sufferings of this kind — the worst it is possible to endure, the doctors say, such as the shrinking of the nerves during my paralysis  and many and divers more, some of them, as I have said, caused by the devil — none of them is of the smallest account by comparison with what I felt then, to say nothing of the knowledge that they would be endless and never-ceasing. And even these are nothing by comparison with the agony of my soul, an oppression, a suffocation and an affliction so deeply felt, and accompanied by such hopeless and distressing misery, that I cannot too forcibly describe it. To say that it is as if the soul were continually being torn from the body is very little, for that would mean that one’s life was being taken by another; whereas in this case it is the soul itself that is tearing itself to pieces. The fact is that I cannot find words to describe that interior fire and that despair, which is greater than the most grievous tortures and pains. I could not see who was the cause of them, but I felt, I think, as if I were being both burned and dismembered; and I repeat that that interior fire and despair are the worst things of all.
In that pestilential spot, where I was quite powerless to hope for comfort, it was impossible to sit or lie, for there was no room to do so. I had been put in this place which looked like a hole in the wall, and those very walls, so terrible to the sight, bore down upon me and completely stifled me. There was no light and everything was in the blackest darkness. I do not understand how this can be, but, although there was no light, it was possible to see everything the sight of which can cause affliction. At that time it was not the Lord’s will that I should see more of hell itself, but I have since seen another vision of frightful things, which are the punishment of certain vices.
To look at, they seemed to me much more dreadful; but, as I felt no pain, they caused me less fear. In the earlier vision the Lord was pleased that I should really feel those torments and that affliction of spirit, just as if my body had been suffering them. I do not know how it was, but I realized quite clearly that it was a great favour and that it was the Lord’s will that I should see with my own eyes the place from which His mercy had delivered me. It is nothing to read a description of it, or to think of different kinds of torture (as I have sometimes done, though rarely, as my soul made little progress by the road of fear): of how the devils tear the flesh with their pincers or of the various other tortures that I have read about — none of these are anything by comparison with this affliction, which is quite another matter. In fact, it is like a picture set against reality, and any burning on earth is a small matter compared with that fire.
I was terrified by all this, and, though it happened nearly six years ago, I still am as I write: even as I sit here, fear seems to be depriving my body of its natural warmth. I never recall any time when I have been suffering trials or pains and when everything that we can suffer on earth has seemed to me of the slightest importance by comparison with this; so, in a way, I think we complain without reason. I repeat, then, that this vision was one of the most signal favours which the Lord has bestowed upon me: it has been of the greatest benefit to me, both in taking from me all fear of the tribulations and disappointments of this life and also in strengthening me to suffer them and to give thanks to the Lord, Who, as I now believe, has delivered me from such terrible and never-ending torments.
Since that time, as I say, everything has seemed light to me by comparison with a single moment of such suffering as I had to bear during that vision. I am shocked at myself when I think that, after having so often read books which give some idea of the pains of hell, I was neither afraid of them nor rated them at what they are. What could I have been thinking of? How could anything give me satisfaction which was driving me to so awful a place? Blessed be Thou, my God, for ever! How plain it has become that Thou didst love me, much more than I love myself! How often, Lord, didst Thou deliver me from that gloomy prison and how I would make straight for it again, in face of Thy will!
This vision, too, was the cause of the very deep distress which I experience because of the great number of souls who are bringing damnation upon themselves — especially of those Lutherans, for they were made members of the Church through baptism. It also inspired me with fervent impulses for the good of souls: for I really believe that, to deliver a single one of them from such dreadful tortures, I would willingly die many deaths. After all, if we see anyone on earth who is especially dear to us suffering great trial or pain, our very nature seems to move us to compassion, and if his sufferings are severe they oppress us too. Who, then, could bear to look upon a soul’s endless sufferings in that most terrible trial of all? No heart could possibly endure it without great affliction. For even earthly suffering, which after all, as we know, has a limit and will end with death, moves us to deep compassion. And that other suffering has no limit: I do not know how we can look on so calmly and see the devil carrying off as many souls as he does daily.
This also makes me wish that in so urgent a matter we were not ourselves satisfied with anything short of doing all that we can. Let us leave nothing undone; and to this end may the Lord be pleased to grant us His grace. I recall that, wicked creature though I was, I used to take some trouble to serve God and refrain from doing certain things which I see tolerated and considered quite legitimate in the world; that I had serious illnesses, and bore them with great patience, which the Lord bestowed on me; that I was not given to murmuring or speaking ill of anyone, nor, I think, could I ever have wished anyone ill; that I was not covetous and never remember having been envious in such a way as grievously to offend the Lord; and that I abstained from certain other faults, and, despicable though I was, lived in the most constant fear of God. And yet look at the place where the devils had prepared a lodging for me! It is true, I think, that my faults had merited a much heavier punishment; but none the less, I repeat, the torture was terrible, and it is a perilous thing for a soul to indulge in its own pleasure or to be placid and contented when at every step it is falling into mortal sin. For the love of God, let us keep free from occasions of sin and the Lord will help us as He has helped me. May it please His Majesty not to let me out of His hand lest I fall once more, now that I have seen the place to which that would lead me. May the Lord forbid this, for His Majesty’s sake. Amen.
The little visionaries of Fatima were also shown Hell. The authenticity of that vision was underlined by the astounding miracle of the sun, seen by tens of thousand of people, even some many miles away (and not subject therefore to mass hallucination) and testified to by atheistic and cynical journalists who attended Fatima on that day to scoff at the children and to disprove the authenticity of the events unfolding there. That terrifying vision of the dammed souls in Hell, though lasting not more than a few seconds according to Lucia, shaped the rest of their lives. They went to extraordinary lengths to fast and make sacrifices for the conversion of sinners to save souls from such a petrifying, hopeless fate.
“Oh my Jesus, save us from the fires of Hell. Lead all souls to Heaven, especially those in most need of Thy mercy.” (Fatima prayer)