[Anguirel]

Hell isn't really as inaccessible as all that in legend. It's getting out that is tricky, but the descent is child's play, through one of the traditional entrances (cf Avernus, The Birdless Place, in the Aeneid.) Virgil puts it best:

"The descent to Avernus is easy;
the gate of Pluto stands open night and day;
but to retrace one's steps and return to the upper air,
that is the toil, that is the difficulty."

(hic labor opus est.)

It seems to me that Tolkien's Hell visions are not at all unlike this. To pick a few examples, Beren and Luthien waltz cunningly, and relatively easily, into the depths of Angband. (Remniscent of Dionysus, who tricked his way into Hades, and the Sibyl, who calmed Cerberus just as Luthien struck down Carcharoth.) But when Angrist snaps and they're fleeing, all such cleverness and subterfuge is scattered to the winds, and they run automatically, only wishing to "see the light again." But for the Eagles, their escape would have been a failure. Being heroes, they get out, but by a hairsbreadth.

The light subject is raised again by the Great Goblin in the Hobbit. Thorin and co. have stumbled almost accidentally into "hell". The Great Goblin orders:

"Never let them see the light again!"

Again, only the divine power of Gandalf enables their escape, in a scene evocative of Christ's Harrowing of Hell.

In Moria, the Dwarves go in willingly, arrogantly, confidently. Their last entry in the Book of Mazarbul is:

"They are coming. We cannot get out."

And in the Paths of the Dead, the Grey Company find the skeleton of, if I recall rightly, Baldor, son of Brego-scratching in vain at the walls of the mountain. Trying and failing to escape, having wandered in so blithely.

Oh, of course the theology is a bit patchy. But the imagery, the poetic and mythic conventions, are all there. Literary hells abound in Middle-earth.