The stories about Atlantis, which has never been found, are supported by myths of great cities destroyed suddenly by rising water. Well, that of course happens extensively all over the world every time there is a pole shift. Cities in the main are established on coastlines and broad rivers, where fish and transportation ease abound. When the massive tidal waves slosh back and forth, these cities do slip under the rising water and are utterly decimated. The cities are destroyed, completely. Buildings that remain are not repaired, as there are no hands to do so. They crumble under the weather, stones eroding and covered by blowing volcanic dust and eventually rooting plants as the endless rains have made the volcanic dust into inviting soil.
On mainland China there are remnants of ancient civilizations, and the stories of their past glory seems to exceed the humble peasantry of today. Was there a great civilization that fell? Yes, as on all continents during the pole shifts, the devastation is so great that cities essentially are brought to dust. China of the past was in keeping with the Chinese people, who are intelligent and diligent. But their development was no more impressive than what they have today. Of course, there are places where today there is but a village, the inhabitants of which can scarce do more than tend to their fields for survival. And if there are traces that indicate a great city once stood nearby, one could postulate that mankind fell. However, after the pole shifts the few survivors regularly migrate, constantly, seeking to escape the gloom and constant rainfall which is everywhere. Of course the survivors disappeared. They went elsewhere.