Technology of the Crystal Tower
As I was running through the Labyrinth of the Ancients this week, an interesting thought struck me and I haven't been able to get it out of my mind: just what purpose does the Labyrinth serve? Now, before you answer "It's protecting the Crystal Tower from intruders", that's not quite what I'm asking. I've been looking around the Labyrinth when I can, and I find it pretty strange that the Allagans would build something like the Crystal Tower for the purpose of capturing solar energy (which even Cid admits is a massive undertaking for them), then build a massive structure around it filled with all manner of traps. If they wanted a giant wall, they could've just built a giant wall. Instead they built it so each each Path has a theme associated with it: Fire, Water, and Poison. There must be an underlying purpose for why the Labyrinth is separated into three discreet Paths with such elaborate architecture, yes?
So with that out of the way, here's my theory: the Labyrinth of the Ancients acts as an energy refinery. The Crystal Tower can collect all the sunlight it wants, but unless it can convert that solar energy into something it can actually use then it's just a toothpick, albeit an exceptionally large and fancy one. So the Crystal Tower gathers the energy, sends it over to the Labyrinth to be processed, and that energy is then used to keep the Tower's systems running. Each of the Paths within thus serves a purpose in this process.
Both the Path of Redemption and the Crossroads have lava constantly flowing through them, so perhaps the solar energy is being converted into thermal energy? The lava is constantly flowing in both of these areas, and beneath the Crossroads is a pit filled with lava that extends for what appears to be hundreds of yalms. Perhaps the Allagans had systems in place that would then convert the thermal energy into fire-aspected aether that they could use.
The Path of Vice could most likely be a heat sink. Should the systems fail, there's an ample supply of water to stop the flow of lava. Also, the water here could be used to make sure that the Labyrinth's systems don't overheat and fail that way. The Path of Decay, meanwhile, could be where any waste from the refinery process is gathered.
Admittedly, I'm no expert in energies nor in how various fuels are refined, but like I said, this is a thought that crossed my mind and I'm curious to see what others think of it. The explanation for all of this stuff could simply be "Because it looks cool." or "No, the Crystal Tower does all that through magic.", but there's nothing wrong with the occasional outlandish theory =P
EDIT: And now that I've read through all of what I wrote and taken a second, perhaps the Crystal Tower does refine the energy it gathers, and the Labyrinth is then entirely a waste disposal facility. Bah, now I'm not sure if I wasn't thinking enough about this and came in half-cocked, or if I'm overthinking it, haha!