Orthodox clerical regions, fixes, and added stuff

common/buildings/00_special_buildings.txt

@@ -6774,6 +6774,8 @@ mount_athos_03 = {
 
 	cost_gold = 1000
 
+	next_building = mount_athos_04
+
 	can_construct = {
 		scope:holder.culture = {
 			has_innovation = innovation_cranes
@@ -6826,6 +6828,76 @@ mount_athos_03 = {
 	flag = holy_building
 }
 
+##########
+# The Citadel of the Theotokos: fourth and final stage of Mount Athos.
+##########
+mount_athos_04 = {
+	asset = {
+		type = pdxmesh
+		name = ep3_athos_monasteries_01_b_mesh
+	}
+	construction_time = very_slow_construction_time
+
+	type_icon = "icon_structure_mount_athos.dds"
+
+	# Unlocked by proclaiming the Athonite Empire. Its decision instantly
+	# consecrates the Citadel; this free building route also handles later rebuilds.
+	cost_gold = 0
+
+	can_construct_potential = {
+		# The fourth stage must not be available before the Empire is proclaimed.
+		title:e_athos = { is_title_created = yes }
+	}
+
+	can_construct = {
+		title:e_athos = { is_title_created = yes }
+	}
+	
+	is_enabled = {
+		scope:holder.rite = {
+			rite_has_doctrine = special_doctrine_is_eastern_christian_faith
+		}
+	}
+
+	character_modifier = {
+		monthly_piety = 0.4
+		cultural_head_fascination_mult = 0.10
+		rite_creation_piety_cost_mult = -0.1
+		religious_vassal_opinion = 10
+		zealot_opinion = 10
+		clergy_opinion = 10
+	}
+	
+	county_modifier = {
+		development_growth = 0.3
+		development_growth_factor = 0.3
+		county_opinion_add = 10
+		tax_mult = 0.3
+	}
+
+	province_modifier = {
+		monthly_income = 0.4
+		fort_level = 3
+		defender_holding_advantage = 2
+		garrison_size = 0.15
+		travel_danger = -15
+	}
+
+	ai_value = {
+		base = 100
+		ai_pious_building_preference_modifier = yes
+		modifier = { # Fill all building slots before going for special buildings
+			factor = 0
+			free_building_slots > 0
+		}
+	}
+	
+	type = special
+
+	flag = travel_point_of_interest_religious
+	flag = holy_building
+}
+
 ##########
 # Sant'Apollinare Nuovo
 ##########