To model the Grisons (Graubünden) aka the land of castles and strongholds, it is almost “mandatory” to include such a structure. Plenty of examples on Google.
I used styrofoam for the ruin of my glorified watchtower, add the stone work with the temp controlled soldering iron, then it gets coated with a special tiling cement - our renovators used the stuff and I got a big leftover gob to try and see how workable it is once it’s dry.
Still needs to be painted, but that’s an assembly line job to get the base colour and then do the highlighting of the stones.