I was exploring around the map on the top floor, near the glass dome area where you could see the lower part of the map, and there was a door, and I couldn't open it. I checked inside there with noclip and immediately went out, don't go there. Although the doors can be removed with the remover tool, it would just show the void and change colors if you walked around it, and you can walk in, but it is ill-advised. I'll show a picture inside the comments.