Best Duchy Buildings in Crusader Kings 3

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Best Duchy Buildings in Crusader Kings 3

Picking your Duchy Buildings is important for the long-term prosperity of your kingdom in Crusader Kings 3. They cost significantly more time and resources than other buildings, and at most, you’ll only have two under your control at once. Even a mighty Emperor is still limited to the personal possession of two duchies. To help you choose the most winning combination, we’ve put together this list of the best duchy buildings in CK3. We’ll discuss what each building does, as well as the overall benefits it provides.

Let’s get started!

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7 Best Duchy Buildings in CK3

Whatever your medieval scenario is, here are the best duchy buildings in CK3!


Royal Armories

The Royal Armory gives you a percentage-based modifier towards the number of levied troops you get from a particular area, while also giving you a maintenance discount for your entire military. This maintenance discount usually only manages to cancel out the cost of the extra levies, but that’s fine. Having more levied troops is always helpful! You don’t even need to actually use your levy, since the other rulers in the game will always factor in how many peasants you could raise overnight when they consider planning an attack on your territory. Levies are just as useful for power projection as they are for defending from raiders, while your men-at-arms mop up any real threats.

Like most duchy buildings, this will cost you around 500 gold per level. It has three levels that all provide increasingly powerful bonuses as you get further along in the technology tree. The top level of a Royal Armory building will give you 40% more levies from the entire duchy. This could amount to thousands of extra men just from having the structure alone.


Tax Offices

A Tax Office is a great pick for vassals’ duchies, or if you’re playing tall or waging minimal warfare with your rivals. Almost every other duchy building will give you some kind of bonus to warfare, but the Tax Office does not. It simply lets you collect more gold from the citizens of the duchy.

Its singular purpose keeps your revenue high, but the effect is proportional to the size and general income of the holding itself. Because of this, you’ll want to place this building in duchies that are already relatively high-income, or at least have the potential to be built up with more cities or castles.

If you’re going to be building tall, a popular strategy involves stacking a ton of gold investment into a small zone. From there, you’ll probably want at least one Tax Office for the sheer amount of gold it can generate. You can always use gold to just buy up mercenaries if your opponents invest in warfare instead!


Royal Reserves

These personalized forests provide bonuses for things like development, tax revenue, and popular opinion. As such, they’re another excellent choice for lands you plan to hand to a vassal in the future. This will make your vassals more valuable and give them more money to spend on their own development.

It isn’t a bad pick for your own land either, especially if you want more diverse benefits than the flat gain of a Tax Office. “Development” as a mechanic handles several small in-game bonuses that can boost your lands. These include higher supply limits, better tax and levy rates, more points toward new traditions for your culture, and more. The Reserves are more of a slow burn than the Tax Office, giving you a wider range of benefits over a longer period of time.

The Royal Garden is essentially an upgraded version of this building, providing prestige and a favorable modifier for stress gain instead of a bonus to development. This modifier is immensely helpful and can be staked with various other traits and perks to avoid stress gain altogether. This opens up more versatility for your rulers with less risk of a reign-shortening mental break. This version is only available with a particular tradition, however.

Note that this is the only kind of duchy building that has a terrain requirement. It’s only buildable in woodland and plains areas.


Siege Works

Staging a siege against your enemies can be one of the most time-consuming and difficult parts of the game. Knowing when to back off from an enemy castle and when to stand and fight can make or break a dynasty. If you’re doing a ton of warfare in your game, the Siege Works are a fantastic pick. These are especially helpful if you’re playing in a part of the world with a ton of small, individual states that need to be pressed together, since it’ll cut down each individual war by a huge amount of time.

Also, handing off an area with a Siege Works to one of your vassals isn’t as big of a deal as one of the other military-focused duchy buildings. Hopefully, you won’t be stuck in a situation where vassals put your major cities under siege long enough to matter. It’s still better than a new vassal getting a defensive advantage with structures you built for yourself! The Siege Works are also more effective than their competition. Buildings like the Archery Range or Blacksmith are only useful for some of your troops, and lose all their benefits if you’re fighting somewhere that those troops lose their effectiveness. Your army will maintain more versatility by specializing in siege warfare.


Leisure Palace

Kicking off the top three in our CK3 best duchy buildings ranking is the Leisure Palace. A Leisure Palace is a good choice for smaller kingdoms, or if your rulers are going to need somewhere to relax. At first, you’ll just build a chateau, which gives some great benefits towards stress relief, prestige, and schemes. Since it’s the only duchy structure that gives benefits to schemes, it’s a must-have for expanding your empire through intrigue and assassinations.

The bonus towards stress relief will let you get more mileage out of holding feasts and hunts. Once you’ve carved out some safe land for a few generations, you’ll want to hold a feast as often as you can afford it. This keeps your vassals happy, and keeps you from becoming too stressed. Stress can break a character, so make sure your rulers take some time off here and there!



The Marches duchy building represents additional walls and security programs being conducted by the holder of the duchy. It makes the entire duchy nearly impenetrable to assault, so it’s an excellent choice if you share a border with hostile neighbors. Nearly every aspect of the zone related to defense will be tipped in your favor. Building a Marches area along with some strong castles, then tempting enemy attackers to get close before pouncing on them while you have a huge defensive advantage is a great way to whittle down the forces of otherwise impossible odds. They’re especially effective in mountainous or wetland provinces like the alps or central Ireland.

You should avoid putting Marches on any duchy that might come under the control of an unfriendly vassal. That, or just avoid letting vassals take the marcher duchies after they’ve been built. They’ll make a rebellion really unpleasant to try and put down. Be on the lookout for other duchies that might have added one of these buildings whenever you’re invading someone new, as well. You might want to find a different angle of attack to avoid the area.


Military Academy

Taking the top spot on our ranking of the best duchy buildings in CK3 is the Military Academy! The Military Academy gives some amazing bonuses to your military. First of all, it reduces the overall cost of the entire military maintenance budget in a percentage-based way. It also gives you access two to more knights per level. But its biggest benefit is the training your knights receive that makes them massively more effective.

It’s easy to underestimate the effectiveness of knights. They appear to be singular characters that are easily overrun when outnumbered, but don’t be fooled. When properly backed up with levies or tough men-at-arms to soak up some damage, knights deal the most damage in the game. Each point of prowess makes them as damaging as ten levied troops! Even better, they don’t cost nearly as much to keep on the field.

Once you’ve become powerful enough that you don’t need to fling every single soldier at every conflict, you can start to raise your men-at-arms and your knights to go forth and decimate the enemy. This way, you can constantly expand through warfare without having to blow all your gold on conscription fees. A fully upgraded Military Academy makes your knights 75% more effective. Stack this with the “train commanders” task for your marshal, and you’ll have a small legion of incredibly powerful elites, ready to tear apart anyone that stands in their path.

Join the High Ground

That’s it for our list of the best duchy buildings in CK3 — thanks for reading! Whether you choose to follow schemes to take down your enemy when they least expect it, lure them into your perfect defensive trap, or blaze forward with a charge of powerful knights at your back, this list should help you out. Let us know your favorite duchy buildings in the comments! Don’t forget to subscribe to our newsletter for more content like this.

Happy gaming!


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