My personal wish would have been a group of Ancients who somehow remembered who they were after the Sundering and decided to build back their city with tech rather than Creation Magic since they had been diminished. That or maybe an Ascian pet project at rebuilding their society in the new world. That is about as likely as a snowstorm in the Sahara though.

Elsewise I have heard everything from it being a nod to Terra in FF9, to it being connected to Azem or Ultima, to it being survivors from a rejoining of another Shard. I have heard that it could be a splinter of Allag as well that just didn't fall when the rest. When I say "I heard", it is just fan speculation I hear about the nets. No one has any concrete info. I just wanted to be clear.

Given the name of the city (Zidane's ability), Zidane's nature, and the fact that there was a sign mentioning souls in the very city, I would at least say that the city has something to do with an ancient species either from the Source, one of the Shards, or even space, who came here and are trying to maintain themselves.

No matter what, it was the first thing I have seen them present from Dawntrail that made me sit up and actually feel some interest, so I can't wait to find out what it is about.