With a company where I used to work, one of my jobs was looking after the ca. 1910 mansion that had become the main offices of the company, a monthly newspaper/ad rag. I was given this task because of a certain knowledge of the building's history, an interest in architecture, etc.
The place was quite haunted. You could feel it in some of the rooms. Just a strong uneasiness, a feeling of "keep moving, get back to where there are people around."
In the mornings, the office workers complained that their furniture was moved, wastebaskets upended, etc. We employed no janitor, and only two of us had keys to the place. The other guy was the owner of the company.
Once, the central wall in which the chimney ran became quite hot to the touch. It was summer, and the heat was not on, so I called the fire dept.
They arrived, and couldn't find any smoke, sparks, flame, etc. We went down to the furnace, which had been shut off and tagged by the gas company as it was an ancient boiler that needed replaced (cracked). It was off. The gas was disconnected. It had no fuel or power source. Yet, it was quite warm to touch. When the others had retreated upstairs, I was alone in the furnace room with my flashlight, and one of the valves began turning on its own. First clockwise, then counter-clockwise.
You hear of your hair standing on end. I felt the hair on my legs press against my socks. All I could think was FLEE!!! RUN!! So I beat it the hell out of there fast, and when I got upstairs the paramedics with the firefighters came forward quickly. I must have been a sight.
We sold the place soon after, and moved into another building, a newer, plain office building. The new owners called me not long after, raving angry that they had not been told of "issues." But I had had no part in the marketing, sale or transfer of the property. The buyer was a lawyer, so the threats and angry exchanges went on for some time after I had stepped out of the situation. They still live there.
Several years ago, when I worked as a tour guide for a victorian home museum, I was coming around from the back of the beautiful old staircase when, to my left out of the corner of my eye, I saw feet in slippers, with a whipsy gown fluttering, padding softly down the stairs. I turned and the image vanished.
In our old home, built around WWI, one can hear voices when there is no one else around or at home. A child's voice usually: "Mommy?"
We also often discover things missing, only to turn up later in a very obvious spot.
This pictures shows one of our dogs (since deceased), with what seems to be a vapor rising in a twin spinning vortex from the floor. You can see through it. I assure you there was nothing like that in the picture when I snapped it. We were in the midst of tearing up the old carpeting to sand the floors. Projects like that usually stir them up.