You have added 'huge' to the list of possible city sizes for Capua in that file that defines the regions (filename eludes me atm, is it regions.txt?), right?

Changes made there only take effect in game at all if you delete the map.rwm afterwards before launching the game (it rebuilds itself on the new data base then)

Although I'm not even sure whether those changes to the regions are savegame compatible at all...