What details of the setting contribute to the horror of the story in "The Cask of Amontillado"?

Clearly the setting is used very effectively by Poe in
this, as in all his fiction, to help create and sustain the mood of terror and horror
that dominates his work. For me, it is highly significant that Montresor takes his
victim Fortuanto ever-deeper into his catacombs. Consider the following
quote:

We had
passed through walls of piled bones, with casks and puncheons intermingling, into the
inmost recesses of the catacombs...

At the most remote end
of the crypt there appeared another less spacious. Its walls had been lined with human
remains, piled to the vault overhead, in the fashion of the great catacombs of
Paris.

It is important to
note how the description of these catacombs contributes to the general feeling of horror
and dread that Poe creates. Upon re-reading the story, we realise that the dead remains
they pass actually foreshadow the unfortunate end of Fortunato at the hand of Montresor.
However, in addition to this, what is really interesting is the symbolic use of the
catacombs. For as we delve ever-deeper we are penetrating not just into the depths of
the Montresor catacombs, but also into the psyche of Montresor himself. At the lowest
depths of the catacombs Montresor takes off his socially respectable mask and reveals
himself for the homicidal maniac he really is, before he presumably goes back above
ground and replaces his mask of social respectability.