If you’re getting invaded or even raided often (hello Vikings), you might want to go for marches which will significantly buff up your defenses in that duchy and all counties in it. I won’t list all duchy buildings here because I already covered them in the video above, but to give you a simple idea of what to go for, here are some of my tips. You can then fabricate a claim to take that county for yourself and secure that duchy capital even if you don’t control any other counties in it, or even if that duchy title isn’t created at the moment in the first place. These will always show you where the duchy capital castle is located and who controls it. In order to quickly identify duchy capitals on the map, simply switch to the duchy map mode view and look for the little emblems or flag icons on the map.

If you can control all counties in a duchy, you’ll be able to not only hold that duchy title obviously, but also institute voting laws to make succession easier (only you can vote). You’ll still most likely benefit from it because they often affect all counties in that duchy. These can only be constructed in duchy capitals so if someone else is controlling it, you won’t be able to pick which building to construct. Whenever you’re a holder of a duchy title, your goal is to control the duchy capital in order to gain an extra building slot where you can construct a duchy building. At the bottom of this page I’ll leave you a link that will show you all special and unique buildings, as well as their locations on the map. Constructing powerful buildings is one of the best ways of reinforcing your lands and making sure they’re less likely to get invaded, raided or contested ( sieged) by other armies waging wars nearby.

Crusader kings 3 special buildings