The Walls of Jericho ... this one will probably be similar to the Siege/Cathar tiles. We have both thought of the same Biblical event here
How to implement? If a player held the 'scarlet cord' card, if they find that they are in the city of Jericho when the walls come down, they would be allowed to score for the city... others occupying at the time do not score... something like that!
I think it would be better to keep this simple, like Cathars. The expansion comes with four tiles, each depicting a segment of the city wall (i.e. any city tile except CCCC). A scarlet cord hanging from a window indicates that this is a siege tile. When the city is completed, it scores only 1 point per tile.