Before the region revamp there were additional buildings there. When you walk around and over where they were it ‘culls’ the polygons that would have been obscured by the buildings.
This is what it does all the time wherever you are, it removes objects you can’t see to keep frame-rate up but it’s still doing it in Fisckebäck in plain sight.
I reported it back in May last year and it’s still there.
I always meant to go there with multiple players and get others to go into the buildings while I moved backwards and forwards to make the buildings disappear.
I was intrigued to see if the character models would still be visible while in the culled building. I suspect not but you never know!