Where is the narrator?

In "The Pit and the Pendulum" by Edgar Allan Poe, the narrator is condemned to death in the Spanish Inquisition. After he is sentenced to die, he wakes up and struggles to find out where he is. Everything is black around him, and he fears that he has been placed in a tomb. He has been in dungeons before, but this is the first that has no light. 

To explore his surroundings, he reaches out with his hands: "My outstretched hands at length encountered some solid obstruction. It was a wall, seemingly of stone masonry— very smooth, slimy, and cold." Though he can feel the wall, he still cannot tell the dimensions of his cell. To do so, he counts the steps he takes pacing from a rag he finds on the floor: "Up to the period when I fell, I had counted fifty-two paces, and, upon resuming my walk, I had counted forty-eight more—when I arrived at the rag. There were in all, then, a hundred paces; and, admitting two paces to the yard, I presumed the dungeon to be fifty yards in circuit. I had met, however, with many angles in the wall, and thus I could form no guess at the shape of the vault, for vault I could not help supposing it to be." Though he knows the dimensions of his cell, he cannot figure out its shape. 

By mistakenly tearing loose some material from the side of the wall, the narrator realizes where he is: "I succeeded in dislodging a small fragment, and let it fall into the abyss. For many seconds I hearkened to its reverberations as it dashed against the sides of the chasm in its descent; at length, there was a sullen plunge into water, succeeded by loud echoes." The piece of the wall that has fallen loose crashes into the water below, and the narrator realizes that a large pit with water lies beneath him. 

When the narrator later wakes up, he is tied down, and he is able to glimpse, with the admission of a bit of light into his chamber, the figure of time on the ceiling far above him. Instead of holding a scythe, the figure holds a pendulum, which the narrator thinks is painted. He then realizes that the sharp pendulum is moving: "There was something, however, in the appearance of this machine which caused me to regard it more attentively. While I gazed directly upward at it (for its position was immediately over my own) I fancied that I saw it in motion. In an instant afterward the fancy was confirmed. Its sweep was brief, and of course slow." The narrator is now between the pit and the pendulum, with no apparent means of escape.