1.29 beta - Spell of making balance issue
So looking at the faction power rating bar, I saw one faction was building the towers. So I declared war and start attacking his cities.
I conquered the city with three of the towers, and here are my potential balance observations.
1. I was able to retain the towers and have them count toward my own spell of making..BUT I hadn't researched the book of mastery yet.
2. Conquering an AI city with towers is far too easy a way to quickly win by spell of making.
So, for balance/challenge, I suggest that when a city with a tower(s) is defeated, the towers should be assumed to have been destroyed during the siege, and the conqueror must start from scratch to build his own.