Your Dungeon Design Is Missing This Medieval Detail

Added: 2026-05-13

[00:00:02][music] >> So, if you've been running old school games for any length of time, you've probably dropped your players into a castle.

[00:00:10]Maybe it's the villain's seat of power, or maybe it's a dungeon with towers bolted on. Maybe it's just there's a big stone structure. Okay, what do you do?

[00:00:19]And here's the thing, there's nothing wrong with any of that. But if you understand how real castles actually evolved over about 400 years, you're going to get a lot more mileage out of that structure because the history of castle design is basically a history of people trying to kill each other more efficiently. And then other people responding to that, and then other people responding to that. And every single one of those design changes is a gift to you as a dungeon master. So, let's get into it. Okay, so we're talking roughly the mid-900s to the 1100s. You've got a new lord who needs to establish control over some territory fast.

[00:00:53]He doesn't have decades. He might have a season before someone tries to take it back.

[00:00:58]The solution is the motte and bailey.

[00:01:01]And it's almost embarrassingly practical. You dig a circle ditch. You pile the dirt in the middle to make a mound, and that's the motte. You put a wooden tower on top of the mound. Then you fence off the larger courtyard next to it. That's the bailey, where your horses and your smithy, your grain, your people actually live and work. The whole thing can go up in days. The Normans were building these things constantly after 1066.

[00:01:24]William the Conqueror's army would roll into a new area, throw up a motte and bailey, and suddenly there's a military presence that's annoying and expensive to dislodge. Now, here's what makes this interesting for a dungeon. The motte and bailey is fundamentally a design about the separation of risk. Normal operations happen in the bailey. When things get bad, you retreat to the motte. The motte is harder to reach, harder to assault, and it buys you time.

[00:01:50]That's dungeon logic you can use directly. If you've got a bandit camp or a goblin lair with any sophistication at all, the Spartan inhabitants aren't just sleeping in random rooms.

[00:02:00]They've got a retreat structure. There's a place to fall back to. The motte-and-bailey model gives you that framework without having to invent it from scratch.

[00:02:08]Okay, so now we're going to upgrade to the stone keeps.

[00:02:12]So, wooden towers have an obvious problem. They burn. You can shoot fire arrows at them. You can literally stack brush against the wall and light it.

[00:02:20]Wood is not a long-term solution for someone who wants to hold territory indefinitely.

[00:02:25]Starting in the late 900s and accelerating through the 1100s, lords who could afford it started building in stone. And the primary form this takes is the keep, a big, heavy, square or rectangular stone tower that's the heart of the fortification. The Tower of London is probably the most famous example. Started by William the Conqueror after 1066, it's this massive square keep. They called it the White Tower, and it was designed to be the last word in a siege.

[00:02:53]It's got thick walls, limited windows, a well inside so you can't be cut off from water, and the entrance is on the second floor, not the ground, specifically to make it harder to force.

[00:03:03]That last point is worth sitting with for a second, so we're going to do that.

[00:03:08]Okay. The entrance is elevated. You come in via an exterior staircase or wooden steps that can be destroyed in an emergency. The ground floor of a lot of these keeps was storage.

[00:03:18]Food, supplies accessed from above. It's not accessible from the outside at all unless you break through the wall.

[00:03:25]This is mature defensive thinking. Every design choice is answering a specific threat.

[00:03:32]How do you breach a gate?

[00:03:33]Okay, we'll put the gate up high.

[00:03:36]How do you starve a garrison?

[00:03:38]We'll store supplies inside.

[00:03:40]How do you burn us out? Well, it's stone.

[00:03:42]Now, for your dungeon, and I want you to hear this, the stone keep logic is about vertical layering.

[00:03:48]The good stuff is not on the ground floor.

[00:03:50]Ground floor is a trap, or empty, or it's a faint. If your dungeon is a repurposed keep, the players who assume the treasure is down in the basement might be missing the point. The lord's chamber was up. The valuables were up.

[00:04:05]Depth isn't always the organizing principle, sometimes it's the height.

[00:04:09]Okay, I want to mention shell keeps quickly because they show up enough that you should know what they are.

[00:04:14]Some lords, rather than building a square tower, took their existing motte and replaced the wooden palisade at the top of the mound with a stone wall. You get a circular oval stone ring on the top of the hill with buildings built against the inside of the wall. Windsor Castle is essentially this, an enormous shell keep that's been developed over centuries.

[00:04:33]The motte's still there, they just replaced wood with stone.

[00:04:37]What does this give you as a dungeon master?

[00:04:40]A round fortification on a raised mound that's open to the sky in the middle.

[00:04:44]That's a distinctive space. Ambushes from the walls, archers looking down into the interior. No clear sight lines across because of the curve of the wall.

[00:04:53]It's very different fight than a square keep. Now, here's where things get genuinely interesting, and here's where the Crusades start to matter in ways that feed directly into castle design.

[00:05:02]European knights and lords who went on Crusades encountered Byzantine and Islamic fortifications that were frankly more sophisticated than what they'd left behind. They saw layered defenses, multiple walls, active defensive systems rather than just passive ones. And they brought those ideas home. So, we come to the concentric castle developed through the late 1100s and 1200s and is built on one central principle.

[00:05:28]There is no single point of failure. You don't just have one wall. You have an outer wall, and inside that you have a higher inner wall, and the space between them is called the killing ground, or the lists.

[00:05:40]If attackers breach the outer wall, and sometimes they might, it happens, they're not inside the castle, they're inside the trap. The inner wall is taller. Defenders on the inner wall can fire down into the lists.

[00:05:53]The attackers are below, exposed, taking fire from two directions, and they haven't actually won anything. Beaumaris Castle in Wales is probably the purest example of concentric design.

[00:06:03]Edward I built it in the late 1200s, and it's almost perfectly symmetrical with an outer wall, an inner wall, towers positioned to cover every inch of the outer curtain, and gates designed so that even if you breach the outer gate, you're in a narrow passage where defenders above can make your life extremely short. This is the design philosophy that should be shaping your high-end dungeons. Concentric doesn't mean confusing. It means layered. It means that getting through one layer doesn't mean you've won. It means the player's victory at the gatehouse is the beginning of the encounter, not the end.

[00:06:36]Think about how many dungeon runs just have a front door and then rooms.

[00:06:41]The concentric castle model asks, "What does the garrison do after the players get through the front door?

[00:06:47]Where's the second line? What's the inner wall?"

[00:06:49]All right, let's talk about towers specifically because they evolve a lot, and that evolution tells you things about how people actually lived and fought in these structures.

[00:06:58]Early towers are square.

[00:07:01]Square towers have a blind spot, the corners.

[00:07:04]If you're in a rounded corner, an attacker can shelter right up against the wall below, and you cannot hit them with anything from above. So, you start to see, especially from the 1200s on, a shift to round towers. No corners, no blind spots, defenders can cover the entire base of the wall.

[00:07:20]Round towers are also structurally stronger. They don't have the corner stress points that square towers do.

[00:07:25]There's a reason the castles that survived in the best shape often have round towers.

[00:07:29]Inside a tower, you're typically looking at a series of floors connected by a spiral staircase. And here's a detail that I love.

[00:07:36]The spiral almost always goes clockwise as you ascend.

[00:07:40]This is intentional. The staircase is a weapon. If you ever put players in a staircase fight in a tower, that's the mechanical reality you can invoke.

[00:07:48]Ascending is advantageous. Defending from above with a right-handed weapon is easier than attacking upward with one.

[00:07:55]That's a real thing, so go ahead and use it.

[00:07:58]All right, the gatehouse deserves its own moment because it becomes over time the most elaborately defended part of the castle. In early fortifications, the gate is the weak point. It's a hole in the wall, and holes in walls are how you lose castles. By the 1200s and 1300s, lords are essentially building a small castle around the gate. You've got towers flanking the entrance. You've got a portcullis, which is a heavy iron grate that drops from above. You've got arrow slits in the entrance passage itself. The gate passage, sometimes called a gate hall, so defenders can fire at attackers who've gotten through the outer doors but haven't gotten through the portcullis yet. You've got murder holes in the ceiling of that passage, openings where defenders above can drop things, pour things, shoot down into the passage. Then in a lot of designs, there's a second portcullis at the far end of the gate hall. You get through the first one, they drop the second one, they drop the first one behind you, and you're in a stone room with holes in the ceiling and arrows coming through all the walls. That's not a defensive position. That's a killing machine that looks like a door. The gatehouse as a dungeon room is massively underutilized.

[00:09:01]Players tend to treat the entrance as a skill challenge. Do we pick the lock? Do we bluff the guards? Do we climb the wall? But what if the entrance worked?

[00:09:09]What if the players talked their way through the outer doors, and then the portcullis dropped behind them, and something changed? The gatehouse is built to be a death trap for people who get confident too early. Okay, so what does this mean for your table? Let's land this. If you're running a castle as a dungeon, whether it's an abandoned ruin, an active stronghold, or something in between, the history we've just covered gives you a set of design principles that make the space feel coherent rather arbitrary. First, castles have logic. Every design choice is a response to a threat. If your castle has a feature, there's a reason it exists, even if the players never know exactly what it is. That internal logic makes the space feel real. Second, retreat is built in. The motte and bailey principle, fall back to the harder position, means your intelligent inhabitants have a plan when the players come through the door. They fall back.

[00:10:03]The fight escalates as the players push deeper.

[00:10:06]Third, vertical layering matters. In a real castle, up is often more important than down.

[00:10:12]The lord's quarters are high, the chapel is high, the treasury might be at the top of the keep, not in the basement.

[00:10:18]Don't let your players assume the game is about going down.

[00:10:22]Fourth, the gate is a machine.

[00:10:25]If your castle has a gatehouse, it should do something.

[00:10:28]It should be possible to get through the outer door and still not be through the gatehouse.

[00:10:33]That tension, that sense that the entrance itself is a design threat, is pure dungeon design. And fifth, the concentric principle. There's always another wall. One layer of defenses not enough for a castle that's meant to hold. If you want your players to feel like they're working for a victory rather than just walking through rooms, build in the second wall.

[00:10:55]Build in the killing ground. Let them win a fight and then realize the real fight is just starting.

[00:11:01]Castle design is 400 years of people thinking very hard about how to make a building dangerous.

[00:11:07]That's free dungeon design content. Take all of it. If you want to dig further into any of this, specific castles, the mechanics of medieval siege warfare, how all of this maps on a specific encounter design, drop your idea in the comments.

[00:11:22]And if you're running BX or old school and you want some tools to help with this, check the Patreon. There's printable material down there that makes your life easier.

[00:11:31]I'm going to go think about spiral staircases now. See you next time.