The Bastion itself? Relatively speaking, it was a more recent addition to Caeleondia's lands. In fact, it wasn't even due to be finished for quite some time... It had its own cores powering it that I heard, but just surviving the Calamity must have taken all of its power...

It was always meant for this sort of thing. Perhaps not exactly so, but if any sort of disaster struck and Caelondian citizens needed a safe haven, the Bastion was meant to be just that.