So, that big wall in zone 5 of DT...
Yes, the WALL one, in Heritage Found. :D
What's its purpose? I skim read through transcripts in the usual places of some main and side quests in this area, checked the Sightseeing Vista descriptions of this map and searched online, but I couldn't find a clear answer.
We know it wasn't on the Source "before", it's made out of a ton of electrope after all (and Erenville says as much on arrival).
I can guess that it would technically make sense to have a wall inbetween the area where people live and a lake made of ruins and lightning explosions. Would be kind of dangerous for kids to play there.
It seems electrope is or was being mined somewhere in the general area. Not sure if they brought the mines with them when they merged or if it's a regrowing resource or whatever though, but either way the wall could contain methods of transportation of the raw product. Or it collects/transport lightning energy, like a lightning conductor but better, and transports that instead. Or both.
(If you wouldn't be able to walk around the wall and people would be living in the place where you can do this, I could imagine Sphene and Calyx wanted to keep scavengers and prying eyes out of old Alexandria, but, well, you can just walk past it, so...)
However, this is all a mix of reasonable assumptions or pure speculation on my end. Anyone here who might know an actual reply, maybe from Q&A on a convention or an interview or so? Or anything in game I might have overlooked, some item description or so?
(It's not a super important question, I know, I'm mostly requiring it for my WoL's head canon and wondering how urgent it would have been to build it. However, I'm also simply intrigued how such a massive wall is just standing there but no NPC bothers talking about it, nor is there a Sightseeing Vista. But it's also not like I'd be busy talking about some basic local infrastructure irl all day unless anyone specifically asks or anything breaks...)