We often see settlements in medieval or ancient times with its cities and castles, etc with walls to protect it from danger and narrow its passage to the settlement to a few gates. However, what would happen if a city has a big enough population that more space is needed, but the walls surrounding it disallow it? Do they just knock it down? It would be easy maybe if it’s just made of wood but not so for ones made of stones. Or they have other methods? Like settling a new city somewhere else?