The most popular legend of Atlantis indicates that the continent sank to the bottom of the ocean. The reason behind the sinking varies depending on the source. The only written history of Atlantis was written by Plato around 960 B.C.
According to Plato, the people of Atlantis lived in a utopian society. Eventually, however, human nature took over, and they succumbed to their greed and hedonistic tendencies. The gods got very angry with this and sent a flood that sank the entire continent. This story is not likely true, but it is still repeated thousands of years after Plato first wrote about it.