OK I have quite a few, but am always reluctant to post about them, but here's one...
In the area my aunt used to live, she started working for a new company (in the 1980s) that had a new-ish building on some old land that had been bought for new development, after being overgrown and derelict for many years.
All was OK, but some of them noticed (after a few weeks in the building) some weird smells outside, like the smell of hair singeing, pork cooking, and the smell of fabric burning. Didn't seem to be anything about that was causing it, and no-one could see anything, or find anything.
Long story short, after several months, they looked into the history of the land the building had been built on. It turned out it used to be a witch-burning point, where a number of women had been burned at the stake several centuries earlier. 😱
Sent a chill right through me when she told me. It was 35 years ago she told me about it. I've never forgotten it! (She left the company after about a year, so I don't know how long the 'weird smells' went on for!)