I think it's just some kind of 3D-structure to loosen up the facade a little bit.:emoji_nerd:
...or maybe is it perhaps another access to rookburgh similar to the door on wuzetown-wall?:emoji_confused:
But when I look at the photo I find the gap in the wall more interesting and wonder what will...
First i thought that an airship could break through the middle of the wall towards the fantasy-area.
But at the moment it could be a banked curve that passes the two recesses in the wall, too. Would be a nice "fly-by" effect for spectators like the loop or the zero-G-roll of Black Mamba in DiA.