The Ultimate Guide to the Best Duchy Building in Crusader Kings 3

In Crusader Kings 3, you can upgrade your duchies by building structures there. These special buildings give the Duchy a massive bonus, allowing you to enhance your land. However, these bonuses are often overlooked because of the cost. So, here’s a complete guide on what Duchy buildings are in CK3, and which ones you should build for your realm.

This guide is current to Update 1.13.0.4.

What are Duchy Buildings in Crusader Kings 3?

Duchy buildings are special buildings in CK3 that provide strong perks and benefits, ranging from increased taxes to even greater military power. These buildings can only be constructed by Feudal, Clan, or Administrative rulers in the De Jure capital of a Duchy and are accessible only if you hold the Duchy title. You also need to right Cultural Innovations unlocked to construct these buildings.

Each Duchy can support only one Duchy building, and these buildings have three levels, each more expensive and beneficial than the last. The cost of these buildings starts at 600 and can increase by an additional 300 gold every level. It takes 5 years to construct or upgrade; this cost is subject to change and depends on your character’s traits and stats. Each Duchy’s count capital has an extra building slot for Duchy buildings.

All Duchy Buildings in Crusader Kings 3, Listed

Here’s the complete list of every special Duchy building with their type in Crusader Kings 3, and why you should build them in your realm.

Duchy Building	Type	Reason
Crown Smithies	Military	If you’ve got an infantry-heavy army, Crown Smithies can be a great choice. They also provide -10% to your army’s maintenance and boost the rarity of any commissioned artifacts.
Archery Grounds	Military	Similar to Crown Smithies, but instead of infantry, you should have more archers. This includes both regular archers and even archer cavalry. You also get a 10% reduction in army maintenance.
Jousting Grounds	Military	If you like using Calavry or War Elephants, then having a Jousting Ground can be quite strong for your stationed Men-At-Arms. Moreover, you get a 10% reduction in army maintenance.
Leisure Palaces	Economy	If you have lower control over a realm or lack Intrigue, this building can be quite effective at making up for that.
Marches	Military	A defensive stronghold that helps you create an impenetrable border. Great to build near hostile regions. Moreover, you get a +30% Holding Tax, which provides a good boost.
Military Academies	Military	Provides a significant -30% reduction in army maintenance, lets you train knights, and create +3 Men-At-Arms regiments. A must-have for almost any playthrough.
Royal Armories	Military	Provides you with an additional 40% Levy Size and reduced army maintenance cost, making it great for aggressive playthroughs. Also provides a 30% boost to any stationed Men-At-Arms.
Royal Reserves	Economy	Increases your Popular Opinion and provides a +30% boost to the Duchy’s development. Provides a flat increase to your monthly income of up to 1.4 Gold. Great choice for an early game.
Siege Works	Military	If you want a strong siege regiment, then you need one of these buildings in your realm. No benefit to other Men-At-Arms.
Tax Offices	Economy	Provides a massive +20% boost to Holding Taxes for your entire Duchy. Must-have if you are having a gold shortage.
Royal Gardens	Economy	Increases your popular opinion and Prestige gain, and adds a 1.4 Gold increase to Holding Taxes. Worse version of Royal Reserves.
Burial Site (Requires Legends of the Dead DLC)	Economy	Significantly increases Control Growth and Plague Resistance in your Duchy. Also provides +1 monthly Piety and increased Legitimacy gain. Great overall option.

Best Duchy Buildings for Early Game

Leisure Palaces are a fantastic early game choice because of their Realm and Duchy modifiers. The bonus to prestige is incredibly good, and because of the sheer amount of stress in the early game, any way to reduce it quicker is better. What’s more, the Leisure Palaces improve scheme’s success chance, making them perfect if you’re planning for lots of intrigue and assassinations.

Best Duchy Building for Warfare

Military Academies are the best Duchy Building if you’re map painting/conquering a lot, because it increases the number of Knights you can wield, making early battles much easier. It also reduces by 30% Army Maintenance, meaning you’ll not go bankrupt waging war early.

Best Duchy Building for Economy

If you’re running short on gold, or have a huge standing army, then building economy Duchy buildings is your best bet. I prefer building Tax Offices as they provide a solid 20% increase in Holding Taxes from all the counties under the Duchy. You should try to build these in Duchies with high overall Development. I pair them with other economy buildings like Manor Houses to maximize the effect of the special building.

Best overall Duchy Building

Marches are the best overall Duchy Building at any point in the game. The sheer range of bonuses make them perfect for your most favorable Duchies. A defensive and offensive choice, getting a bonus to supply limit, levy reinforcement rate, and garrison size is huge. And the slow down in raid speed makes it perfect to allow you to react to any hostile invasion.

For more on Crusader Kings 3, check out What is Cultural Acceptance in Crusader Kings 3: Royal Court and how to increase it on Moyens I/O.