Why?
These doors are seen in none of the periods between 12000 B.C. and 2300, so one would assume they were re-invented, not survivors of the apocalypse, given that they are also integrated directly into the domes. But Zeal was a magic-powered kingdom, while the Future is pretty much shown to be technological. There has to be some kind of connection between these.
I would theorize that Lavos' emergence in 1999 may not just be because of him effectively being a ticking time bomb. He delivers a presumably smaller although still devastating barrage when he emerges in 12000 and obliterates Zeal. Is it possible that the inhabitants of the Future recreated the Mammon Machine and were using Lavos-Powered Technologies, and this is what provoked Lavos' rise?




















