For modern-city like I intend the renaissance movement where new town born en-masse and poor's flee the poor countryside to the rich city. At Roman time city was not really rich: they host some rich but most of it's population was poor, only commerce give a bit of wealth in cities.
Roman's was more traders and peasants with everything gravitating around the army than "citizens". Probably a modern-city comparison can be for the USA the "west" vs the "est", where in the west surely there was cities, witch in reality are "villages" for our modern lingo and people live more on trade and peasant's activities than else while the "east" was already a urban-centric civilization. I hope that's clarify a bit my view.
About urban replacement: honestly in the past "replacement" was far different than today, they build piled rock buildings, replacement happen after a war or in case of big incomes using the same rock and adding some. That does not really change the cities, that change was more addictive and slow rebuilding...
Roman's was more traders and peasants with everything gravitating around the army than "citizens". Probably a modern-city comparison can be for the USA the "west" vs the "est", where in the west surely there was cities, witch in reality are "villages" for our modern lingo and people live more on trade and peasant's activities than else while the "east" was already a urban-centric civilization. I hope that's clarify a bit my view.
About urban replacement: honestly in the past "replacement" was far different than today, they build piled rock buildings, replacement happen after a war or in case of big incomes using the same rock and adding some. That does not really change the cities, that change was more addictive and slow rebuilding...