I believe the Ancients were nomadic people, travelling all over the world. They did settle in some locations, namely the Forgotten Capital. Those who settled and gave up the Ancient's way of life are referred to as 'traitors' by Sephiroth in the Nibelheim Mansion basement.

Ifalna lived in the Icicle Inn, but there's no mention of her birthplace.

I would assume the majority of Shinra employees are from Midgar. It's a vast city, but we only see a very small part of it in the game.