User blog comment:Xilinoc/Ch. 632 - friend 2/@comment-1210805-20150625093733/@comment-10630156-20150625102758

I got a crazy theory that the Quincy world was Hueco Mundo until the war when the quincies where defeated the first time and then it was destroyed and made into the Hueco Mundo that we know, some Quincies managed to escape to the human world as this was going down. Hence the old building that was under Los Noches and the ruins they where at in 544.

If this is true then I'm interested to see how Kubo would play this.