You patch a few holes and put together a simple assembly for converting the motion of the "waves" to electricity to keep the light on. You have no idea how it was originally supposed to be powered. The tower itself honestly isn't in bad condition, though, definitely not as bad as Kuviu described in his dream. But the stele was totally destroyed, then, so it must have been in the future.
The thing is, it's not a flimsy tower. Whoever built it was a better architect than you. Unless an entire building smashes into it, you're certain it will last for millennia. You find yourself wondering how long ago this place was built. And whether that's even a cogent question in the Furthest Ring.