I imagine it wouldn't have pulled things down, if it spreads into the city proper, it would just start rearranging things up there, as well (and the people in the area would start to follow the laws of the Cult as a social attack.)<br/><br/>My assumption was, since most of the Old City is leftover first age artifact architecture, it would be pretty resistant to the magic; the New City would probably change eventually, too.<br/><br/>The area effected by the Prohibition Index will continue to grow until there are no more people in the area to influence or until someone wipes out the cult / eradicates the teachings/ideology.<br/><br/>I imagine it's up the storyteller to determine just how far-ranging the Charm's effects are at the start of the game.