Hexcrawl Design, Using Scale and Finding Things

A major consideration for a DM designing a hexcrawl is going to be the scale of the hexes. It's should come as no surprise a 6-mile hex is small then a 30 mile hex but a lot of rules for outdoor adventure don't' take the actual scale of hexes used into consideration while most D&Dish games do have very clear rules tied to a likely scale of 10 feet (maybe 5) to a square. The rules do tell you how long it may take to search a 20 x 30 room and provide the rules for resolving such a search, but they don't do that for a wilderness hex.

A note on hex sizes: when I speak of hex sizes I'm using a measure from flat hex-side to flat hex-side.

A 20 x 30 foot room is a fair sized room in a house,  it's an unremarkable room in the average dungeon but we can come to grips with it's size the size of a hex can be tricky to get into ones mind for modern folks used to traveling at 55mph (or more) and the rules don't' help much. Let me go back to a 10 mike hex; there's about 86.5 square miles in a 10-mile hex. A ten mile hex would fit a little more then 2.5 Manhattans. A 30 mile hex is about 777 square miles, that would hold 23 Manhattans.
Walking back and forth in a 20 by 30' room(in a 10' wide path)  would take a normal man in D&D less then one turn. Walking though all of the whole hexes of a ten mile hex subdivided into 1 mile hexes at a rate of 20 minutes a 1-mile hex would take 30 hours (when was the last time you walked for 10 hours? have yuo ever walked for 10 hours?).

Path through the 90 one mile subhexes in a 10 mile hex.

Now come the questions relating to that walk: How many encounter checks would be made walking that path? What would PCs see on that path? How often would a party have to rest walking that path? How woudl those factors vary by terrain?  All of those questions should have some answer that could be drawn from the rules that you use to build your hex crawl.

Another question:What would be the chance of finding an entrance to a dungeon in that hex? The smart-ass answer- About the same as finding a doorway in two and half Manhattans, a really big doorway but it would be a chore wouldn't it? The real answer would involve how fast you are traveling, who is looking, and what's actually obstructing visibility. If there's a fire going at the dungeon entrance and not much obstructions, haze, or wind you might be able to spot the smoke at the dungeon entrance from 20 miles away. Not surprisingly most dungeon dwellers don't keep a signal fire burning at the dungeon entrance (do the occupants cooks or keep warm however?). So what are the odds? Not sure yet.

Let's look for something bigger, like a town. There's going to be smoke and fields surrounding a town but an olden days town is itself likey not all that large, a square mile or two fits a whole lot of stuff.
A town and immediate environs might fill 7 of the sub hexes on the sample map above, there'd be enough room for about a dozen towns (assuming you could feed everyone). Based on area the stumble across chance to spot a town would be 1 in 12 walking though the whole hex, use the search path above however and the chance becomes 100% eventually.

Using the rough estimates above we can now make a few rough guesstimates for game mechanics and finding things in a hex. 1 in 12 to find a small town assumes a blind path, folks have eyes and ears that's got to at least double the odds for finding a small town. There must be road leading to the town (at least some local cart tracks) that's got to double chance as well, a town is a busy place and everyone doesn't stay inside there will be other signs (and smoke mentioned above) if we double the chance again we've climbed to a 8 in 12 chance of finding that small town in a hex with non-nondescript terrain. The chance will surely decline with dense foliage, and a mountain in the way, it would also decrease if the party is keeping on the down-low to avoid be spotted by locals or moving hastily, we can build those actions and features into a table for a hexcrawl.

The sample above gives a possible way to handle actions of a party and the chance to find a feature based on it's size and importance. Travel rates would get worse in rugged terrain as would the chances to finf things, I'd likely  halve them for difficult terrain and halve it again for very difficult terrain. Local guides and familiarity should add to the chances.

If we are using a larger or smaller hex the odds would change. In some scales there woudl be no chance to miss some features. A city is pretty easy to find in a 3 mile hex but could still be missed in a 30 mile jungle hex. A specific hamlet in a large densely populated hex may just as hard to find for a stranger as it would find the same sized place in a dense jungle at night.

Scale of each hex in a hexcrawl will have an impact on play over how fast the map can be crossed. It will impact what can fit in each hex and the odds of finding features in a hex.