It seems obvious to me that Atlantis was North and South America.
These have been at the top of my list for quite a while...until recently. I'm leaning to Sundaland in SE Asia now.
The only (surviving, known) ancient source for the Atlantis story is Plato, and one of the details that suggests inside info of some sort is the remark that, west of Atlantis, one would have found islands, and following those, one would come to the land that could most truly be called a continent -- the Americas.