I’m thinking about megadungeons at the moment, and thinking about the smallest possible unit in a megadungeon, because I know level doesn’t work for me as a smallest unit because I have trouble with a scope of perhaps 10-12 rooms at a time. It occurred to me in the car the other day that geomorphs-type units might be a good way to do this: It’s more interesting to me than designing a dungeon 1 room at a time, but I’d still need a bunch of them to actually make up a whole level. For those purposes, I wanted to figure out what a good size in terms of squares will work for me, for maximum utility.

I thought a good place to start would be Gygax’s generators. Delta looked at the AD&D DMG Appendix A and came up with these categorisations:

• Small — Up to 200 square feet (10×10 or 10×20). Small living quarters or chapel.
• Medium — Up to 2,000 square feet (from 20×20, 30′ diameter around, to 30×60 or 40×50, etc.). Tower central room, guard hall, castle kitchen, big living quarters.
• Large — Up to 20,000 square feet (from 50×50, up to 50×100, max 100×200). Keep great hall, largest DMG Appendix A room/ chamber/ cave size.
• Huge — Up to 200,000 square feet (from 100×200, 150×350m, max 400×500). Major cathedral, largest DMG Appendix A cavern size.

To clarify in terms of modern equivalents at the top end of these ranges, a small room is master bedroom sized, medium is lecture hall sized, large is about the size of an Olympic ice skating rink, and huge is 4 football fields. The chances of rolling a 20 000 square foot room using the AD&D Appendix A generator is around 0.01%, which means you’ll get it once every 10 000 rooms or so, and the chances of rolling a 2500 square foot room are in the range of 3.5% (about 3 out of 100 rooms), although it’s tricky for me to calculate the chances of room sizes between 2500 and 15 000 because of the choices Gygax made in said appendix.

Basically, as likelihood was important to me, I’d change Delta’s analysis slightly because my primary goal isn’t description:

• Small — Up to 200 square feet (10×10 or 10×20). Small living quarters or chapel in a dungeon, bedroom or master bedroom in modern contexts. 16% of rooms.
• Medium — Up to 2,000 square feet (from 20×20, 30′ diameter around, to 30×60 or 40×50, etc.). Tower central room, guard hall or barracks, castle kitchen, big living quarters in a dungeon, university lecture hall in a modern context. 74% of rooms.
• Large — Up to 5,000 square feet (from 50 x 50 up to 50 x 100). Keep great hall or church, or basketball court in a modern context. 10% of rooms.
• Huge — Up to 20,000 square feet (from 50×50, up to 50×100, max 100×200). Cathedral or cave room, Olympic ice skating rink in a modern context. Closer to 0% of rooms than 1%, but perhaps 1-in-1000 rooms.
• Massive — Up to 200,000 square feet (from 100×200, 150×350m, max 400×500). The whole castle or cathedral grounds, four football fields in a modern context. Actually 0% of rooms, which is fair because this is a ridiculous size. But, if you wanted a village in your dungeon, this would be the size to pick.

If I want my geomorph to be able to fit a large room, then I’ll need to make it a square number, so 5041 square feet, which is 71 feet to a size. That’s 14 x 5 foot squares to a side. Nightwick Abbey, my touchstone for geomorph-based dungeons, is 10 x 5 foot squares to a side, and I was expecting a larger geomorph here, because I effectively want to fit a conceptual set of rooms in each geomorph — the entire base for a faction, perhaps, or at least a significant section of it. It needs to be a geomorph, though, so I need to think about exits. Most 10 x 10 geomorphs have potential exits at 3 and 7. If I have a larger geomorph, it would be better to have 3 potential exits than 2, so a 15 x 15 geomorph makes more sense, because I can have exits at 4, 8 and 12, with 3 squares between each one. That puts our geomorph area at 5625 square feet, which means we can fit a large room as well as some hallways or secret spaces if we so desire. Coincidentally, this makes the size of a geomorph roughly the half of a tennis court on one side of the net, which is easy to visualise. A neat side-effect of this size is that I can fit a huge room in a 2 x 2 grid of geomorphs, so if I wanted to randomly generate them (this wasn’t my plan), I could reasonably include this as a rare chance, but more importantly, it should fit in with other geomorphs. I’d need a 5 x 7 grid of geomorphs to hit close to the massive size cavern, but that’s supposed to be ultra-rare anyway.

That’s basically my working for an AD&D inspired geomorph. I’ll throw my mathematics here at this point, and then come back to it:

All that in mind, I’ll revise my criteria because mapping:

• Small — 4-6 squares. Small living quarters or chapel in a dungeon, bedroom or master bedroom in modern contexts. 16% of rooms.
• Medium — 8-20 squares. Tower central room, guard hall or barracks, castle kitchen, big living quarters in a dungeon, university lecture hall in a modern context. 74% of rooms.
• Large — 21-75 squares. Keep great hall or church, or basketball court in a modern context. 10% of rooms.
• Huge — 4 geomorphs or 300 squares. Cathedral or cave room, Olympic ice skating rink in a modern context. ~1-in-1000 rooms.
• Massive — 20 or more geomorphs or 1500 squares. The whole castle or village or cathedral grounds, four football fields in a modern context.

Or, if you still want to randomly generate, it would look something like this, with the rule being you continue rolling, drawing as you go, until you can’t draw the room you rolled inside the 15 x 15 square geomorph, and then stop.

Ok, there’s my little dungeon geomorph process. Was it worth it? Definitely not, I should’ve written a review.

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