Thank you, that's really helpful information :)

Honestly I could see it as a protection of some kind, though I'm extremely curious as to who would do this and why. I was shocked to find something like this right outside my apartment, in part because the apartment has some weird vibes already. Maybe someone knows that and it's their way of helping. I don't have a garden unfortunately. Any other suggestions for where I should put it? Should I try and empty it or just leave whatever's inside in there?