Fort, Motte, & Bailey

[gollum]

Just guessing, but there must exist a trigger atfer building the first fort upgrade (or as you say the upgrade is the trigger) that activates the elevated series of castle maps.

As far as i know in the VI campaign (and various medieval era mods i've played) it works the same.

[caravel]

That's odd. The game must keep track of the upgrades that were built even when superseded by a keep...

[drone]

I'm guessing it triggers on the Motte building then. There are no upgrades for the pre-Fort "castles" in VI. Maybe the game sets a variable on the Motte being built and the map is chosen from the hilltop set after.

I guess one test would be on provinces that have a pre-built Keep at the start. This should be flat, but if a Curtain Wall is built, does it become a hilltop Keep? This would verify that it triggers on the first possible upgrade, or just a Motte.

[gollum]

Originally posted by drone
This should be flat...

Not necessariliy, for example Constantinople is set on a hill although it starts as a Citadel. The map series choice have been pre-made but apparently it was still a choice as to what series of maps was chosen.