Base game achievement

Monumental

Fully upgrade a Duchy Building anywhere in your personal Domain

Conditions as the game checks them

Possible decides whether the achievement can still be earned in a run; happened is the check that unlocks it (common/achievements/_achievements.info).

Unlocks when (happened) (8 lines of game script)

custom_description = {
	text = monumental_achievement_trigger
	any_directly_owned_province = {
		has_building_with_flag = {
			flag = fully_upgraded_duchy_capital_building
		}
	}
}

As written in game/common/achievements/standard_achievements.txt.

The file gives no “possible” condition for this one.

Source: game/common/achievements/standard_achievements.txt, game/common/achievement_groups.txt and the English localisation, Crusader Kings III 1.20.0.3. Unlock share: Steam Web API, 2026-10-02.