To begin with only the most obvious. Dante and Virgil walk the whole thing. Solid base that. Yes, the same could be said of John Bunyan's A Pilgrim's Progress , but I haven't read that, so it would be a shorter comparison. Furthermore, if we accept north as up and do irreparable damage to my integrity as a former behavioral geographer, then Melanie is indeed hiking up, much as Dante and Virgil are.
Angels simply litter the place.
Comparisons can be overly picky. Beati pauperes spiritu not to mention pauperes analogi . Imagine a Everest-sized hole on the antipodes of Everest, and then make both of them a lot lot bigger. You don't even get up to Purgatory proper until you've hiked out of the Earth's atmosphere. That kind of big.