Have you ever explored any creepy places, like a haunted house, some temple ruins or an abandonned hospital?

When I was younger I used to love going around with people to go explore old shut down factories, train stations, boarded up houses, construction sites or large patches of woods and forests, and all sorts of places like that. Here in Québec I even checked out an old hospital and an abandoned army base.
I’ve given this up today because I’m too old to get arrested for trespassing, but it made me wonder if anyone here ever explored anything cool. And it can be anything really, don’t stick to my examples. Anything you visited and that you thought was awesome and maybe a little creepy.
I always got all excited and we always had fun, but I was always somewhat dismayed when my exploring partners were too scared to go in certain parts, like basements and all, but then I never went in on my own.
Whatever the circumstances and by whichever means you went exploring, how did you feel?