in a recent game, i vassalized zara after taking his holy capitol of Aksum and 2 other best cities. His city of Lalibela settled 4 north of the capitol however provided constant culture pressure on Aksum, forcing me to keep a very large garrison in Aksum to prevent revolts.

So I'm wondering how culture would have worked out if I had taken Lalibela and then liberated it back to him (if that's possible, I think it is, though I seem to remember a situation where I wanted to give a city to a vassal and couldn't). Would all the old culture from Lalibela continue to pressure Aksum? I assumed it would which was why I didn't do it that way.

In retrospect I wish I'd just bloody razed Lalibela and resettled there, he never reached friendly with me anyway and I was in WFYABTA with him all game, worthless vassal. I didn't want to take the time to finish him off though, I just wanted to use those troops elsewhere right then.