I wasn't quite sure where to put this, but Haunted Workplace seems the most appropriate.
I work in a modern retail complex (less than 10 years old) on the edge of a very old medieval English town. As far as I can tell it's built on land that's been open since at least the 19th century, although it has older medieval boundary walls, house plots and pathways on the 3 sides of the site.
It is a cavernous building with high open roof spaces with exposed heating/ air conditioning/ water pipes. Wherever a ceiling was not not strictly necessary there isn't one, the staircases are also open. The acoustics are weird, very deadened especially when it's closed and there's only a small night team on site. I'm guessing from what I've read about before there's a bit of an infra sound issue going on - the acoustics do remind me of empty tube stations,. Ever since I've worked there I've seen figures but dismissed it as products of the infra sound. It happens most often when it's closed and I'm working, but almost every shift I see figure standing out of the corner of my eye, when I look there's nothing, often related to some background pareidolia-like effect where a discarded jacket or stack of crates has taken human form. None of this bothers me or feels ghostly in any way, I just ignore it and get on with my work.
However a few spots do feel a bit weird but no unexplainable experiences, and so far I've just listened out for any odd stories from staff who've worked there longer than me and up to now had heard nothing.
Then about 2 weeks ago I had a genuinely odd experience while outside in the yard. It's quite open and large with high overhead lighting, a very tall medieval wall on one side, the building on 2 (several stories in height), the 4th side a high modern fence and security gate. I have been out there at night almost every shift at some point and never felt anything before. I was placing some items into a store unit when I saw a figure peering around a van at me, about 20ft away (there's a few parking places for company cars/vans in the yard). This was very different to the "figures" I'd seen out of the corner of my eye inside the building. I looked round, and it seemed to pull itself back behind the van, before looking around again when I looked away. No figure I'd seen before had moved at all, let alone in such a human way. There also seemed to be something a bit off about it/him. He was a similar height to me (around 5'6") but very wiry and slight, with a very pale, very rounded bald head and seemed to be wearing some kind of sandy coloured jumpsuit or dungarees that made me think of desert fatigues.. He was solid, but seemed very wispish and insubstantial somehow. After this had happened several times I decided to go and have a look - I'd need to walk past it to go back in anyway, and I could walk forward to see round the back of the van while staying about 10ft away. I don't think I'd have been keen on just poking my head round at close quarters. As I drew level and looked across I had a fleeting image of a figure but what I actually saw was a human sized column of dense, white mist, that rapidly shrunk into a a small roughly circular swirl about 5ft off the ground, then just disappeared. The mist was not transparent I couldn't see through it at all, in fact it was very white almost pearly.
Certain aspects of it reminded me of the one time in my life I genuinely believe I saw a ghost (recorded on these boards somewhere) but it felt very different in the sense the "ghost" I saw before had a vivid sense of being a human consciousness. Although it was certainly conscious, aware of me and interacted with me, it definitely did not feel human. Didn't feel "alien" either, whatever alien is. It also didn't feel scary or dark, probably best described as neutral or mischievous, there was that kind of feel to it. If anyone has read the Stephen King book "Insomnia" it did put me in mind of the little bald doctors, only he was more a normal human size.
I didn't tell anyone just reflected and thought I need to log in and post this - then this week something else happened. I was inside in a a room with a colleague. I had my back turned with the door about 6ft away to my left. My colleague was on the far side of the smallish room. I saw a man walk past me, through the door and up into the corridor beyond, wearing our work clothes apparently - I turned and left shortly afterward closing the door behind me on an empty room I thought. Only the door opened almost immediately with my colleague wondering why I had shut the door in his face. There was no one in the corridor. I apologised and said I saw someone leave I thought he had already gone. This lead to a number of interesting conversations. Basically I found out multiple staff members have seen a man in the same area of the building, walking into and out of rooms mainly. Also have seen objects flying off of shelves, they've assured me not just falling, but flying with enough force to hit the opposite wall when there's no one near by.
This is the opposite end of the building from the yard where I had the other experience (which I still haven't told anyone at work I decided it just sounds too weird!) It does seem a bit strange that they both happened within a week of each other. I also got some pretty wild stories of deaths and old buildings that apparently used to be on the site but I can't find any evidence for what people have said so far though I'm going to do more research into it.
Also interesting that after working there for several years and hearing nothing I'm only just finding out a large number of colleagues have had odd experiences and seem to think the place is haunted.
I suspect a lot of it is down to the infra sound thing which I'm sure is a factor. It's also possible from the known geography that an underground river could run under the site somewhere which could also add to the weird acoustics in there.
Anyway, any thoughts on any of it, especially the little bald chap, would be most welcome, and I'll let you know if I find out anything more.