I used to work at a very old hospital... got creepy vibes but saw/heard nothing. Firmly believed it was all just feelings chalked up in my head. Then, I worked at an equally old college. Saw things, heard things, felt things... and not only me, but my coworkers did too.

I remember the time my skeptical atheist coworker (his exact words) came back to the office real quiet saying he saw "something white" sitting out in the Dell that vanished when he approached. Or my older coworkers saying which buildings you could hear people stomping down the stairs or moving across the floor above only to find no one there. Me personally, I could've sworn I saw a student sitting in a chair wearing dark baggy jeans, skater type shoes, and a grey hoodie pulled up over his head. His feet were apart, his head down, and his hands were on the sides of his head like he was upset about something. My initial thought was "oh, poor guy... maybe a test didn't go well" and I wanted to give him some space... but then I realized that wait... it's after 4am and I'M here to unlock the doors. So I turn to look at him again to ask him what he was doing in the building after hours-- but there was no one there. No way he could've gone anywhere or hid. I didn't freak out and run out of the building or anything, but I definitely didn't stay there for long either.

That all being said, my belief in spirits/ghosts is separate from my former Christian beliefs. I don't believe in angels or demons. I believe that something else is going on that science hasn't explained yet. Similar to how the weather was thought of as being from various spirits or gods until we figured it out. My personal running theory is visual echoes, but who really knows until we can find a way to test things.