At what difficulty does the AI cheat?

[Daynarr]

Originally posted by Taqwus:
I think I've gotten Fortified Cities from events, actually -- isn't that the "city builds a ring fortress" one?

Hmm, never got that event but it's possible.

Not sure what are reasons behind such AI-don't-like-building-castles behavior but I remember seeing that discussion in another thread earlier (somewhere at the time when game was released). I guess main problem is how to make AI realize what is best time and place to invest in building castles.