It is of faith that Heaven exists for the good and Hell for the wicked. Faith teaches that the pains of Hell are eternal, and it also warns us that one single mortal sin suffices to condemn a soul forever because of the infinite malice by which it offends an infinite God.
St. Anthony Mary Claret
Then shall he say also unto them on the left hand, Depart from me, ye cursed, into the eternal fire which is prepared for the devil and his angels:
Matthew 25:41
If I ascend into heaven, thou art there: if I descend into hell, thou art present.
Psalms 138:8
For if God spared not the angels that sinned, but delivered them, drawn down by infernal ropes to the lower hell, unto torments, to be reserved unto judgment: And spared not the original world, but preserved Noe, the eighth person, the preacher of justice, bringing in the flood upon the world of the ungodly.
And reducing the cities of the Sodomites, and of the Gomorrhites, into ashes, condemned them to be overthrown, making them an example to those that should after act wickedly. And delivered just Lot, oppressed by the injustice and lewd conversation of the wicked. For in sight and hearing he was just: dwelling among them, who from day to day vexed the just soul with unjust works.
The Lord knoweth how to deliver the godly from temptation, but to reserve the unjust unto the day of judgment to be tormented. And especially them who walk after the flesh in the lust of uncleanness, and despise government, audacious, self willed, they fear not to bring in sects, blaspheming.
2 Peter 2:4-10
"Depart from me, come not near me, because thou art unclean: these shall be smoke in my anger, a fire burning all the day"
Isaias 65:5
For the Lord Almighty will take revenge on them. In the day of judgment he will visit them: for he will give fire and worms into their flesh, that they may burn, and may feel for ever"
Judith 16:20 -21
Oh, what strength has not the fear of Hell to rein us in from sin! To that end has **God created Hell. **He has created us, and redeemed us by His death, that we might be happy with Him; He has imposed upon us the obligation of hoping for eternal life, and on that account encourages us, by saying that all those who hope in Him shall be saved. For none of them that wait on Thee shall be confounded. [Ps. 24:2] On the other hand, it is His wish and command that we should be in fear of eternal damnation. Some heretics hold, that all who are not in sin should consider themselves as assuredly just and predestined; but these have with reason been condemned by the Council of Trent (Sess. 6 can. 14, 15), because such a presumption is as perilous to salvation as fear is conducive to it. And let Him be your dread, and He shall be a sanctification unto you. [Is. 8:13] The holy fear of God makes man holy. Wherefore David begged of God the grace of fear, in order that fear might destroy in him the inclinations of the flesh. *Pierce Thou my flesh with Thy fear. *[Ps. 118:120]
St. Alphonsus Maria de Liguori, Bishop and Doctor of the Church
I looked up in terror and saw in the distance someone racing down the path at an uncontrollable speed. I kept my eyes on him, trying to identify him, and as he got closer, I recognized him as one of my boys. His disheveled hair was partly standing upright on his head and partly tossed back by the wind. His arms were outstretched as though he were thrashing the water in an attempt to stay afloat. He wanted to stop, but could not. Tripping on the protruding stones, he kept falling even faster. “Let’s help him, let’s stop him,” I shouted, holding out my hands in a vain effort to restrain him.
“Leave him alone,” the guide replied.
“Why?”
"Don’t you know how terrible God’s vengeance is? Do you think you can restrain one who is fleeing from His just wrath?"
Meanwhile the youth had turned his fiery gaze backward in an attempt to see if God’s wrath were still pursuing him. The next moment he fell tumbling to the bottom of the ravine and crashed against the bronze portal as though he could find no better refuge in his flight.
"Why was he looking backward in terror?" I asked.
**“Because God’s wrath will pierce Hell’s gates to reach and torment him even in the midst of fire!” **
St. John Bosco
A fire is kindled in my wrath, and shall burn even to the lowest hell: and shall devour the earth with her increase, and shall burn the foundations of the mountains.
Deuteronomy 32:22
Where is hell? Some were of opinion that hell is everywhere, that the damned are at liberty to roam about in the entire universe, but that they carry their punishment with them. The adherents of this doctrine were called Ubiquists, or Ubiquitarians; among them were, e.g., Johann Brenz, a Swabian, a Protestant theologian of the sixteenth century. However, that opinion is universally and deservedly rejected; for it is more in keeping with their state of punishment that the damned be limited in their movements and confined to a definite place. Moreover, if hell is a real fire, it cannot be everywhere, especially after the consummation of the world, when heaven and earth shall have been made anew.
Catholic Encyclopedia