In the last cutscene with Cid for the quest Like father, Like son Cid says "Aye, it happened. The Crypt of Xandes I lies in the depths of Silvertear Falls."
Which should read: Aye, it happened. The Crypt of Xandes it lies in the depths of Silvertear Falls. What you saw took place there, when van Darnus finally tracked me down. I thought myself as good as dead.
It seems to make more sense to me.