A factual city lost to time.

Plato said Atlantis existed about 9,000 years before his own time, and that its story had been passed down by poets, priests, and others. The founders of Atlantis, he said, were half god and half human. They created a utopian civilization and became a great naval power. Their home was made up of concentric islands separated by wide moats and linked by a canal that penetrated to the center. The lush islands contained gold, silver, and other precious metals such as orichalcum and supported an abundance of rare, exotic wildlife. There was a great capital city on the central island.

Atlantis itself was destroyed by a large fragment of a comet 10,500bc in our timeline also called the younger dryas event, the whole of North America at that time was under a massive sheet of ice several miles thick and when the comet struck the ice melted ands raised the sea waters around 250-300metres so it was that Atlantis was sunk beneath the waves.