I remember back in the day, me and a friend played a Civ 5 game where I build my unique improvement in thier land. This was years ago. However I am playing a game now (Just with AI) and I can no longer do this. It says you can't build an improvement outside of your territory. I have open borders with the civ. The same thing is also happening with city states that I am allied with. Does anyone know if this is something that was adjusted in a patch, or could it be a mod doing it? I'm using tons of mods. I can still build roads/railroads, but not farms, my unique improvement, etc.