Montresor's vaults are described as being dark, wet, and foreboding. Initially, Montressor carries torches down into the catacombs because of the extreme darkness of the vaults. Fortunato follows Montresor down a winding staircase until they reach the damp ground of the vault. Montresor then comments on the "white web-work" on the cavern walls. Fortunato then takes note of the "nitre" on the walls of the cavern. Nitre is another name for potassium nitrate, which is a white crystalline salt that is often used as fertilizer and a constituent of gunpowder.

As the two characters descend further into Montresor's catacombs, Fortunato mentions that the vaults are extensive. Montresor then comments on the numerous piles of bones, "casks and puncheons intermingling." Montresor also mentions that the nitre hangs from the walls like moss and tells Fortunato that they are underneath a riverbed. This information explains the dampness of the catacombs and indicates that the vaults are deep underground. The end of the vaults are described as a dark crypt, where the "foulness of the air" causes their torches to glow. Three of the walls are aligned with human remains to the ceiling, and there is a small depression in the back wall, where Montresor locks Fortunato inside as he gradually buries him alive. Overall, Montresor's catacombs are dark, extensive, damp, and filled with piles of human bones.

The vaults are very damp and encrusted with niter, a crystalline salt used to make gunpowder, as a fertilizer, and in medicine. They are also very large because this is where the dead bodies of family members are laid. Montresor reminds Fortunato that his family is very large. As they are walking, Montresor tells Fortunato to "observe the white web-work  which gleams from these cavern walls." He continues, saying, "We passed through walls of piled bones, with casks and puncheons intermingling." Casks and puncheons were used to store the wine, so the catacombs have several uses. "We are below the river's bed. The drops of moisture trickle among the bones." Not only are the catacombs very large, they go down very deep below the surface. "We passed through a range of low arches, descended, passed on, and descending again, arrived at a deep crypt, in which the foulness of the air." As they go further down, the smell of the air changes and smells bad. We are reminded that the Montresors do punish those who offend them.