Encountered what I think is a bug, possibly connected to the "Fortifications" module.
In my current game the Barbarians built a city on the Tower of Eyes. The Mind Mana remained, but the Tower itself was no longer there. I'm playing as the Elohim, so having a Unique Feature disappear was disappointing, since I was hoping to get control of it at some point and receive the associated Trait.
I thought it might be connected to the "Fortifications" module, since I remember reading that that module made the Tower of Eyes claimable as a Fort. And of course I know that cities can be built on Forts/Castles/Citadels. So I think that that's what might have happened, but I'm not a programmer, so not sure.