The city was constructed with canals and locks to control the water level. With pump mechanisms such as a windmill, they drained out the crater to expose more usable land. The city was structured with concentric sea walls around a central Temple, surrounded by a central lake that was somehow elevated from the rest of the city.
The Atlanteans were a secretive people who would capture any boat that passed by, keeping the city secret for millennia. The captured crew would be forced to live as second-class citizens for the rest of their lives.
Many of those refused to live as captives and formed an underground resistance with the aim to escape the island around the Kalos Kalyre of BC 1262.
The Quo'thalas attacked the island that day to claim it. The sea wals were destroyed and the city was flood. The Cyrollans, in order to deprive the Legacy of the Sosiqui destroyed the central temple. One of the survivors was Sinclair.
The first mention of Atlantis was by Plato in his works Timaeus and Critias, presented as a utopia somewhere in the Western ocean. It wasn't sure whether Plato was talking about the lost continent or fabricating an elaborate concept to help prove an argument, as he was known to do. There have been several underwater ruins discovered since the early twentieth century that had thought to have been Atlantis but the estimated dates of the ruins were nowhere near to the hypothesized date of Atlantis's existence.