Oh, this one took me some deep thinking to be able to answer!!! As far as personal significance for Kaia, Gridania is a huge one ( as far as residential areas go ) due to the fact that she's made a name for herself there as White Viola and it's there she meets the core people who inevitably change her life for the better.

And of course, the final zone in Endwalker holds a HUGE impact on her considering the sacrifice that she ends up making to help her Warrior of Light progress ( going out with her husband at that! ) where the reflection of her acceptance kicks in and she's willing to do whatever it takes to help. It reflects her growth as a character compared to where she started and it's absolutely an area that makes me emotional when I think about Kaia and where she started vs where she is during that point of MSQ.