Descent into Hell!!! Rarrr!...Well, sort of...

[davem]

I'm not sure that the Paths of the Dead was a strict allegory of Hell. In 'The Rivers & Beacon Hills of Gondor' Tolkien gives some background to the place:

The Men of Darkness built temples, some of great size, usually surrounded by dark trees, often in caverns (natural or delved) in secret valleys of mountain-regions; such as the dreadful halls and passages under the Haunted Mountain beyond the Dark Door (Gate of the Dead) in Dunharrow. The special horror of the closed door before which the skeleton of Baldor was found was probably due to the fact that the door was the entrance to an evil temple hall to which Baldor had come, probably without opposition up to that point. But the door was shut in his face, and enemies that had followed him silently came up and broke his legs and left him to die in the darkness, unable to find any way out.

So, it was originally the site of a temple of Sauron (Morgoth?) worship. Of course, this was a later writing, & so we can't necesarily take this as being in Tolkien's mind when he wrote LotR. We do know that Tolkien expressed a dislike of Dante's theology (whether William's obsessive love of Dante played a part in this is anyone's guess...)

And what reason Baldor had for wanting to get in there (did he know there was such a temple beyond the door?) is another question...