In a user created Ace Combat 4 campaign: https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=2939726351&searchtext=Ace+Combat

There are several instances of buildings being placed on an angle relative to the ground. So rather than a skyscraper going straight up, it goes 45 degrees or even 90 degrees. Two notable uses of this are Stonehenge's guns, and tunnels.

How is this done? The map editor does not seem to provide a way of doing this and I can't find anything online.