
It seems like the Arena isn't recessed into the ground... but Google said that "Hole" means

Maybe I'm misunderstanding something?
P.S. I suspect that "possessiontile" is the cell that the cursor points to when hovering over a building in general (but I'm not sure). At least for the Library, this cell is located OUTSIDE the Library itself. But for the Arena and the Tower of Marlet, it's located at coordinates x-0, y-0 for some reason. It's unclear. =)

P.S. P.S. I looked it up, and the Arena can slightly sink into distorted areas of the landscape... maybe that's why it has the "Hole" marking.