Buildings are a great way to secure the prosperity and security of your realm for the long-term in Crusader Kings 3. There are quite a few to choose from and, especially in the beginning, you'll have to think about which structure to build and when, due to the hit your treasury takes. This can make it easy to overlook Duchy Buildings which, although more niche than their regular counterparts, provide some rather strong bonuses.
CK3's Duchy Buildings are one way in which you can specialize your realm and labeling any one as the best is rather impossible. They can improve a variety of aspects, from levy size, to individual unit damage, and the amount of taxes you receive from your subjects, while also improving the holdings in said Duchy.
Crusader Kings 3 Best Duchy Buildings
Each Duchy has a De Jure capital County, and each capital County has an additional building slot in its Barony. You can identify these Baronies by switching to the Duchy Titles map mode and looking for the shield symbols. Just remember to click the Barony behind it, rather than the symbol itself.
This slot is marked with a golden outline and four arrows in each corner, all pointing inwards. Only the owners of the Duchy title can build Crusader Kings 3 Duchy Buildings and reap their benefits. Building them also requires first unlocking certain Innovations.
Holding too many Duchies can incur a large opinion penalty from your vassals, and chances are you will spend the majority of your game limited to only a few of them. Wars and succession can also see Duchy Buildings slipping away from you, but this is a normal part of the game, especially at first.
Duchy Buildings in Crusader Kings 3 take 5 years to construct, by default. They start at level 1 and can be upgraded all the way to level 3 for increasing bonuses, at the base cost of 300, 400, and 500 gold, respectively.
Here are the boons they provide, as of the game's Azure Patch 1.4. Realm modifiers apply to the holder of the Holding in which the Duchy Building is constructed. Duchy Modifiers apply to all Holdings in that particular Duchy, while Holding Modifiers affect only the Holding in which the Duchy Building is placed.
Archery Grounds
Realm Modifier
- Increases Archers Damage and Toughness
- Increases Skirmisher Damage, Toughness, Screen, and Pursuit
- Reduces Men-at-Arms Maintenance
Blacksmiths
Realm Modifier
- Increases Spearmen Infantry Damage and Toughness
- Increases Heavy Infantry Damage and Toughness
- Reduces Men-at-Arms Maintenance
Jousting Grounds
Realm Modifier
- Increases Heavy Cavalry Damage and Toughness
- Increases Light Cavalry Damage, Toughness, Screen, and Pursuit
- Reduces Men-at-Arms Maintenance
Leisure Palaces
Realm Modifier
- Increases Monthly Prestige
- Speeds Stress Loss
- Increases Own Hostile Scheme Success Chance
- Increases Own Personal Scheme Success Chance
Duchy Modifiers
- Flat Increase to Monthly County Control Growth
- Percentage Increase to County Control Growth
Marches
Duchy Modifiers
- Increases Supply Limit
- Increases Levy Reinforcement Rate
- Increases Garrison Size
- Increases Hostile Raid Time (slower raids)
- Increases Defender Advantage
- Increases Fort Level
Military Academies
Realm Modifier
- Increases Knight Limit
- Increases Knight Effectiveness
- Reduces Army Maintenance
Royal Armories
Duchy Modifiers
- Increases Levy Size
Royal Reserves
Duchy Modifiers
- Increased Development Growth
- Increased Popular Opinion
Holding Modifier
- Flat Tax Increase
Siege Works
Realm Modifier
- Increases Siege Weapon Effectiveness
- Increases Siege Weapon Toughness
Duchy Modifier
- Increases Fort Level
Tax Offices
Duchy Modifiers
- Increases Holding Taxes
As we mentioned before, it's hard to point at one as being the best, since each building caters to a certain playstyle and can be a good response to situations you didn't anticipate when first starting your playthrough.
Nonetheless, early on, you might be tempted by the Military Academies to get extra, more powerful Knights, as they do make a difference in wars. Their relatively flat progression, however, doesn't leverage your growth well.
Royal Armories are also worth considering, as they increase the Levy through the entire Duchy by 20/30/40%, adding up to thousands of extra troops becoming available. Levy units aren't the best, but they do make up the bulk of all armies, so gaining a guaranteed extra castle or more worth can make rebellious vassals think twice.
That's what you need to know about Crusader Kings 3's Duchy Buildings. For more help with the game, check out our guides on dynasty and innovations.
Original article written by Matthew Ralphson, later additions by Bogdan Robert Mateș.
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