This story is told from the first person limited point of view. The narrator is a prisoner being held in captivity during the Spanish Inquisition until conquering soldiers come and rescue him.
The fact that the narrator doesn't know much about his surroundings while in the pit and has to grope around to "visualize" his situation increases the sense of horror (especially when he almost falls into the pit unaware).
Check out the following references for more details concerning Poe's use of point of view in this particular short story to create effect.
The story is told in first person. Because it is first person and we have to follow the narrator we know the same amount about his surroundings as he does. We learn things when he learns them, see things when he sees them, and feel his emotions when he feels them.