Excellent thread - great reading! I used to go "roguing" (as we called it) around abandoned houses all the time in my carefree youth. The only time anything strange happened was in this house. (Picture taken at that time; back in the early 80s.)

Friends of a friend were living in the one story addition on the right side of the house that had been the servants' quarters. They were living rent-free and looking after the property for the owners. They had keys to the main house and told us we were free to explore as long as we were careful not to break anything. It was an amazing house; fully furnished with all its contents undisturbed since the owner had died sometime in the early 60s.
The story we were told was that the owner's children could not agree on what to do with their deceased parents' estate and it had been allowed to just sit for over 20 years. I seem to recall that the family name was something like Lee or one of those other Virginia names that rhyme with
history and in this case:
money. Apparently the heirs were well off enough to allow what must surely have been, even back in the 80s, a multi-million dollar estate, to just languish.
The room off to the right in the picture below was the library. I still have dreams about this room - good ones, though. It was too dark to take pictures in since I didn't have a flash but it was lined with leather-bound books and drawers full of old maps. There were lots of maps from WW I showing detailed troop positions and trenches somewhere in France that had to have been originals - in English, French and German. There was one of those German helmets with the spike on top, guns, a bugle, flags, and thousands of letters. I feel certain that the deceased owner must have been a high ranking officer in the AEF.
Most of the furniture was Victorian and very posh looking but there were a few rooms with cheaper looking furnishings from the 40s and 50s. Nothing had been removed - the closets were still full of clothes and the pantry was stocked. My friends and I had lots of fun exploring the first two floors, joking and laughing and trying to play the bugle. It was a cold but bright sunny day, as you can see in the picture.
I was the first one to venture up to the third floor. At the top of the stairs the first door I came to opened on a large room, painted light blue and jumbled with children's furniture. It had a large fireplace which was filled with dead birds. The whole room was full of dead birds. The sun was streaming in through those three smaller windows (on the right side in the photo) but the room was freezing. And the air in the room was impossibly still and just said DEATH.
I wasn't exactly frightened, but I had to get out of that room immediately. I warned my friends but they had to experience it for themselves. I left the house immediately and waited in the yard. We thanked our hosts for the tour and had a very quiet and introspective ride home. It was weeks before we felt like discussing the "room with all the dead birds" but we all had similar reactions.