It is clear that the impact of the house and its environs on the narrator who tells us this curiously fascinating story is one of horror and gloom and doom. Setting in Gothic fiction is a key factor that is of the utmost importance, and note how Poe uses the house and its surrounding landscape to create a forbidding tone that foreshadows the evil and depression that the rest of the story contains:
I looked upon the scene before me... with an utter depression of soul which I can compare to no earthly sensation more properly than to the after-dream of the reveller upon opium--the bitter lapse into everyday life--the hideous dropping off of the veil. There was an iciness, a sinking, a sickening of the hert--an unredeemed dreariness of thought which no goading of the imagination could torture into aught of the sublime.
Note how this description helps to set the tone of this short story at the very beginning of the tale. Both the narrator and we, the reader, automatically have our mental faculties impinged upon by the doom and gloom of the house and its setting, and this helps us to understand how Roderick and Madeline are the way that they are because of their long-term residence in a place that is obviously so bad for the soul.