A quest exclamation mark on the minimap in the City Square map in the Atlas

A quest exclamation mark is displayed on the minimap and map overlay in the City Square map in the Atlas:



When a character moves in its direction it disappears on a definite distance.

Here to report the same exclamation mark in the same spot. I assumed it was part of a questline or some such so I did a nearby excavation, first, but when I was done with the excavation the mark was gone. Moving further away from the point doesn't appear to restore the exclamation mark for me. I believe this side square is where my portal into the map originally was, and I don't recall seeing the mark when I had first arrived.

I ran a lot of City Squares I think it was last league (for Metamorph farming) and saw it on both that side and the opposite side. I just assumed it was a hideout that was removed/not implemented.