Citadels are fantastic for wartime, but what about peace time? I was confronted with a small problem in a recent game of mine, when the ONLY coal in my continent (which I had conquered completely, and wasn't a small one) was next to a CS. Unfortunately for me Alex had already allied with it (I wish I knew the map like him), opened Patronage, and in a few words it needed something like 2000 gold to ally myself. Plus, it would be a continuous draining of money, trying to compete Alex on a CS he wants.
Fortunately, the coal was only two tiles away from my border - so a citadel was created, capturing this tile plus (accidentally) the lux tile next to it; the city was left with no strategic and no luxury resource, and of course completely hated me (I thing it was Angry -50, or something like that). BUT I didn't stage a war, had no diplo hit, AND Alex completely lost his interest - some turns later I even got ally to that city, staying in this state till the end...
Fortunately, the coal was only two tiles away from my border - so a citadel was created, capturing this tile plus (accidentally) the lux tile next to it; the city was left with no strategic and no luxury resource, and of course completely hated me (I thing it was Angry -50, or something like that). BUT I didn't stage a war, had no diplo hit, AND Alex completely lost his interest - some turns later I even got ally to that city, staying in this state till the end...