Nothing, it probably just had enemies come up through them.
Yeah, there is no basement rendered under the arenas.
I think the elevators actually go up, to bring people to the stands to watch the PVP instead of participating.
The center of the map is the only area that is completely removed from the game, it’s basically an empty square/hole when you go there. So I’d guess that will be real, paid DLC Area. There’s a shit ton of room underground they could put all kinds of stuff if they wanted. I haven’t checked if there is any current used area underground at the the same spot as the above ground cloud. There’s other cloud areas they could put new areas in too. I’m guessing the center piece had to just be removed cause it got started on but not finished yet? Idk, it’s just speculation at this point.
Im guessing you’re right about the arenas having different rule sets too. No real reason to have three unless there’s some technical reason to try to load balance the areas. I wouldn’t think that’s necessary with how instancing works but I’m not knowledgeable in how that shit works in games.
Didn't know that about the center area, figured it was just a great big ocean. If there's a giant empty square there, then yeah, it's probably gonna be DLC. That isn't a ton of space though. A new island there would be roughly...half the size of Caelid? Already a smaller area.
I'm thinking the Land of Reeds is the best candidate for a large-scale DLC of some sort. They could even just save that for Elden Ring 2 and make it a massive place. IMO the Land of Reeds is the most interesting part of Elden Ring's world that isn't actually reachable in the game.
What I'd do:
DLC 1: The center island / new area + Godwyn the Prince of Death / maybe arenas
DLC 2: Underworld expansion into a lot of the unused space + Miquella the Unalloyed / lore development for the Formless Mother
DLC 3: Land of Reeds (off the map entirely, take a boat there) + the Formless Mother
A fight with Ranni somewhere in there to get that last rune could be cool too. DLC 1 I'd have be an island with a small city made of gold. DLC 2 would be whatever underworld ideas can be conjured up. DLC 3 would be far-eastern themed, lots of samurai etc.