It's called hostile architecture and it's things like arm rests in the middle of a bench so you can't lie down on it, or sloped windowsills so you can't sit there.

I once saw a bench with a statue of a person sleeping on it. Wtf?

"To prevent the unsightly possibility of someone sleeping on this bench, we should put a statue of someone sleeping on this bench! Leave the useless bench there but also fuck you!"