There's also a certain amount of "and then you're done" here. Maybe one day we'll decide to raise Miami or New Orleans, but once all of your cities have raised

There's also a certain amount of "and then you're done" here. Maybe one day we'll decide to raise Miami or New Orleans, but once all of your cities have raised themselves out of the swamps they were built on, you don't need to keep raising them for tradition's sake. You're done. And new cities, such as they are, we no longer allow to build below grade in swamps.