You look through the round window of the door and see that the iron fence that surrounds the grounds of the large house connects to the side of the guest house just to the right of here. So this door allows access to the woods on the north side of the house.
You twist the doorknob and push but the door doesn't budge. Maybe the door frame has become warped over the years? You push harder and it seems that the door is about to come open. You move back a little and then push into the door harder with your shoulder. The door moves a little more, but then suddenly, with a tremendous jolt, it slams back against you with a loud bang! You stumble back a few steps and feel a burst of cold air in the room.
It seems that someone or something doesn't want you going through that door.
Aaaah! I'm outta here!