Relationship between Bahamut and Midgardsomr?

[Nalien]

One thing to be careful about when speaking of Eorzean geography is that the Calamity rearranged the land somewhat. The Crystal Tower could have been built relatively far from Silvertear Falls, but after the land shifted due to an artificial moon crashing into it and then a giant dragon exploding like a nuke, the two locations could have been pushed together.

I don't think the geography changed that much. The only things which have really moved were the Twelve Stones, entire locations didn't swap places, the Calamity mostly just caused some "superficial" scars to show up. Even the most drastic damage/movement (the Descent in lower La Noscea) isn't nearly as substantial as Crystal Tower moving from, lets say South Shroud to Mor Dhona. It would also have had to have moved other places, like Saint Coinach's Find, which is directly connected to the Tower by a road (interestingly does anyone else also notice a road leading to the Lake as well?), which just seems very unlikely to me. Then there is the placement of Omega; NPCs even speculated that Darnus chose that location to drop Dalamud so that Omega could be dealt with and not be a potential threat to Bahamut, indicating that, prior to the Calamity the area was "known" to have Allagan Ruins. Given Omegas role and Dalamud and Crystal Towers relationship, it makes sense that it would be situated close to the Tower.

The Calamity did more unearthing that causing drastic movements, I think. Eric even gave us a pre-Calamity idea of where the Tower was; Exactly where it is now.