The setting is vital to the story, from the bizarre descriptions of the carnival and then the gloomy vaults. Poe’s interest in describing the horror of the vaults is to cultivate a mood of repulsion and dread. One might raise the question of how Montresor could have kept the cement wet enough to work with a trowel during the time before he brings Fortunato into the vaults, but perhaps that would be unfair to the work as a whole. It is interesting to note the description of the walled area where Montresor imprisons Fortunato: “a still interior recess, in depth about four feet, in width three, in height six or seven” (paragraph 68). This wall recess corresponds fairly exactly to the measurements of a grave.
The setting of the Cask of Amontillado has a great impact on the overall impression of the storyline, as well as the perception of the characters actions and personalities. For example, when Fortunato is first introduced in the story, he is described as being in motley and with a jester's cap, which is a symbol of his foolishness and his intoxication problem (this is what led them into the crypt in the first place, to search for a cask of Amontillado). The setting of this moment supports this perception because they are at a carnival, which not only distracts people from wondering where Fortunato and Montresor have gone, but also symbolizes that the night was already crazy and full of frivolity. When they arrive in the crypt, the molds that cling to the wall, the stone blocks that pile in the area and the corpses that line the perimeter help the reader fixate on the idea of being trapped, as well as providing foreshadowing to the situation (Montresor seals Fortunato in the burial site using these stones).
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The setting has a big impact on the story. If Montresor had not have brought Fortunato to the catacombs, Montresor would have failed his plan- for he would be alone, and the servants- who were supposed to be there and sneeked away- would not have any proof. The fact that Montresor brought him into the catacombs, brings the story to life- showing how mystique and cleverly Montresor unfolds the plan- no one opening Fortunato's grave for centuries. The main setting is contributes to the entire story, for he does his murder without a single soul knowing.