Love this myself, Catholic Encyclopedia's entry for Hell:
"The existence of hell is proved first of all from the Bible."
Nothing in the Bible can prove itself anymore than something in a Harry Potter novel proves the existence of elves, unicorns, or trolls. Next...
"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...
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. As to its locality all kinds of conjectures have been made; it has been suggested that hell is situated on some far island of the sea, or at the two poles of the earth; Swinden, anEnglishman of the eighteenth century, fancied it was in the sun; some assigned it to the moon, others to Mars; others placed it beyond the confines of the universe [Wiest, "Instit. theol.", VI (1789), 869]. The Bible seems to indicate that hell is within the earth, for it describes hell as an abyss to which the wicked descend. We even read of the earth opening and of the wicked sinking down into hell (Numbers 16:31 sqq.; Psalm 54:16; Isaiah 5:14; Ezekiel 26:20; Philippians 2:10, etc.). Is this merely a metaphor to illustrate the state of separation from God? Although God is omnipresent, He is said to dwell in heaven, because the light and grandeur of the stars and the firmament are the brightest manifestations of His infinite splendour. But the damned are utterly estranged from God; hence their abode is said to be as remote as possible from his dwelling, far from heaven above and its light, and consequently hidden away in the dark abysses of the earth. However, no cogent reason has been advanced for accepting a metaphorical interpretation in preference to the most natural meaning of the words of Scripture.
Hence theologians generally accept the opinion that hell is really within the earth. The Church has decided nothing on this subject; hence we may say hell is a definite place; but where it is, we do not know."
CATHOLIC ENCYCLOPEDIA: Hell
Logically, if you don't know where something is, you can't say for sure if it's real. That's basic physics. Without observing a particle directly you can't measure its properties or say anything definitive about it. It's the Heisenberg Uncertainty Principle. If they knew absolutely Hell was real, they'd know where it was and what it's like.
If Hell is real and contains fire it has to have an atmosphere (fire requires oxygen to burn.) So it'd have to be on or in a planet. Could it be the center of our Earth? Sure. Is it? Best answer I've found is my own, "I don't know - I've never died before."
Personally though if Hell is 'being removed from the sight of God' the only thing we know of in the universe that meets that defintion is a black hole where even light cannot escape, so very much removed from the sight of everything else even God.