Nobody can comprehend it
Veronica Giuliani abbess of the monastery of Città di Castello and Italian mysticism considered among the most important contemplative penitents and her model was Franciscan spirituality. She wrote the diary "The Hidden Treasure" in which she recounts her own experience.
"In a sudden, I found myself in a dark, deep and smelly, you heard bulls, braying of donkeys, lion roars, whistles of snakes, ghastly confusion of voices, and thunders that contributed great terror and fear. I saw flashes of fire and dense smoke. I cried out for help, but nothing!
Isaiah 34:10-15 "It will not be quenched—day or night. Its smoke will ascend forever. From generation to generation it will lie desolate; no one will ever again pass through it. The desert owl and screech owl will possess it, and the great owl and raven will dwell in it. The LORD will stretch out over Edom a measuring line of chaos and a plumb line of destruction. No nobles will be left to proclaim a king, and all her princes will come to nothing. Her towers will be overgrown with thorns, her fortresses with thistles and briers. She will become a haunt for jackals, an abode for ostriches. The desert creatures will meet with hyenas, and one wild goat will call to another. There the night creature will settle and find her place of repose. There the owl will make her nest; she will lay and hatch her eggs and gather her brood under her shadow. Even there the birds of prey will gather, each with its mate.
I seemed to see a big mountain all covered with snakes, the snakes and reptiles braided together, no one recognized the other, and in quantity without a number.
Beneath them, I heard curses and ghastly voices, I turned to my angels, I asked them what those voices were, and they told me that there were many damned souls, and that this place was their prison. At this point it opened immediately, the great mountain, and I seemed to see it all filled with demons and damned souls! In large numbers!
The damned souls and demons were stuck together as if they were one, and the demons were connected with the damned souls with chains of fire as if the demons and souls were the same thing though every soul had so many demons upon which could not be counted. The way in which I saw this I cannot describe it, but I understood, but I do not say anything of what it is.
Suddenly I was transported to another mountain where bulls and horses were unbridled which continuously and viciously but one another. These demons issued fire from their eyes, mouth and nose, they had swords and sharp teeth that seemed to be devouring and chewing up some type of objects into pieces. I then suddenly realized that these were SOULS of the damned with the clash of their kicking and devouring the souls, what terror it was. Do not ever stop and realize that this last forever.
Then I saw other mountains with most ruthless torments, but it is impossible to describe, and the human mind can never, ever understand. In the midst of this place, there is a horrible throne, high, broad, and composed of demons! There is a horrible struggle, in the middle of the devils throne as the demons who make up this horrible throne are always warring with each other.
The chair is made up of mostly demons, the head and the principal. Here it is sitting, Lucifer, ghastly, horrible. O God! What can describe such horror! More horrible and ugly than all other demons. Satan seems to have a head the size of a hundred heads, and it is full of very long spikes on top of each of which there is like an eye, big as a head of cattle, which sends arrows fire burning all of hell. And although this is a very big place comprising innumerable damned souls and demons, all see Lucifer without veil no matter where they are tormented Lucifer is always seen by all, and all in hell are suffering the same torments over seeing Lucifer. Lucifer sees all, and everyone sees him.
Here, my angels, made me understand that, as in heaven, the sight of God, face to face, makes everyone infinitely happy and blessed, those in hell, will forever have the ugly face of Lucifer, this diabolical monster. They see Lucifer, face to face the enemy of God at all times to their ever lasting horror, and having lost God forever, and ever, they will only know horror.
Lucifer stands out so that all the damned always sees him to their horror. Lucifer cursed and blasphemed all, it is all cursed and curses, and it haunts, and torture all for eternity. And how long is this? I asked my angels, and they answered me: Forever, for all eternity. O God! I cannot say anything, of what I have learned and been made to understand, with words, we do not have words in our way of understanding.
Here, now, I saw something that filled me with horror. The cushion in the chair of Lucifer, that was seated in that throne. It was the soul of Judas! And under the feet of Lucifer was a very big cushion, all torn and horrible. I was made to understand that these were souls of bad Religious who performed their duties to our Lord's Church poorly and Lukewarm; suddenly the throne was opened and I saw among numerous demons that were under the chair, a large amount of what appeared to be animals.
Then I asked my Angels: Who are these? And they told me that they were prelates, Head of the Church, and the superiors of Religion. O God! Each soul suffers, all the damned souls of others torment each other, and I seemed to be made to understand that my being there was a torment to all the demons! And all the souls in hell.
I will not say more, because I cannot say anything. All I said is nothing, and everything I've heard from the preachers in the Church is nothing. The human mind and soul does not have the ability to portray the horrors, pains and torments of hell.
In hell there is a place for everyone, and there is still my place, if I perform my duties bad or commit even one mortal sin without Confession.. May everything be all to the glory of God, according to the will of God, for God, God!
It seemed then that I heard screams and voices of lamentation from the damned. I saw infernal monsters, many serpents, many ferocious animals, and an infernal stench and extremely hot flames, which were so big that their height could not be measured. I could only compare it to the distance between heaven and earth. As far as the size of the place, one could not see the beginning or the end, it was so vast.
You could hear many blasphemies and curses against God. How sad. What torment this caused my soul.” After that I was shown hell once more: “At that moment I was once again shown hell opened; and it seemed many souls descended there, they were so ugly and dark that they struck terror in me. They all dropped down in a rush, one after the other, and once they had entered those chasms there was nothing to be seen but fire and flames.”
This led me to offer myself as a victim of Divine Justice: “My Lord, I offer myself to stand here as a doorway, so that no one may enter down there and lose Thee.” Then I stretched out my arms and said, “As long as I stand in this doorway, no one shall enter. O souls, go back! My God, I ask nothing else of Thee but the salvation of sinners. Send me more pains, more torments, more crosses!”
May the Holy Spirit guide you in understanding this message