I'm playing as Spain when for some reason Mvemba declares a surprise war on me at about turn 40. After I destroy most of his army and capture his nearest city, I decide it's time for peace. Except first I harvest the copper from a tile within the occupied city's borders, taking the cash, and then, oh yes, I give the city a much more appropriate name. After that, in exchange for all his gold and all his luxuries, I gladly give the city back to him. Of course, the AI being what it is, that new name is never changed for the rest of the game.