Estimates vary, of course, but it’s predicted that sea levels could rise as much as eight feet by 2100, and while that might seem like nothing, it would make a huge difference to the cities of the United States. A rise of even a foot could put some cities underwater; although maybe not quite to the extremes of the Atlantean legend that that phrase conjures up. Instead, rising sea levels are predicted to cause ‘chronic and disruptive flooding’ - that is, enough constant flooding to make parts of the city permanently uninhabitable. So get booking your trips to these fifteen US cities - you may not be able to visit in another few decades' time.