In the current multi-player game I am playing with my friend I built Louvre and got 2 Great Artists. Now, when I built the wonder in my idle city I was thinking about just using them for Golden Ages but how about this... Make an invasion onto the enemy's landmass, culture-bomb the beachhead and use a great general to set up a citadel? This should make it much harder for the enemy to push you back. Citadels dont work on enemy land, right? But they SHOULD work inside your cultural borders, even if it is disconnected from the rest of your empire? Would such a set-up work and how useful do you think it would be?