I read an interesting wargaming post last week, which combined with recent consideration of wilderness games has caused me to reconsider the importance of wilderness terrain. In previous campaigns I have been guilty of speaking primarily in biomes; you're in a desert, or a swamp, and maybe there's a multi-hex feature like a river but for the most part sub-hex detailed terrain has not made it from my brain to the players. This is problematic.
Part of it is probably a scale problem, and part of it is an improvisation problem. Obviously I cannot reasonably subhex-map every hex through which the party passes; as a result I must improvise and then record those improvisations for later consistency (hills don't tend to just disappear). But improvisation is difficult when one lacks a good sense for the thing one is improvising; I suppose this is probably why Tao does research the way he does. This task is made more difficult by man's alterations; how common are glades in pristine woodlands? What does unaltered topograhy look like, without roads carved through it and sections flattened? I honestly don't know.
The problem of scale is that I don't really know how big things are in terms of six-mile hexes (~24 square miles). Fortunately google maps can help with this one a little. Turns out the parts of Pittsburgh with which I am familiar, centered somewhere between Downtown and Oakland, fit right about in a six-mile hex. Frick Park to Downtown (or "dahntahn", as they say) is about 5.8 miles on foot. The literal topographical Squirrel Hill is two or three miles across, and something like a mile and a half north-south, rising to a height of about 350 feet over the nearby lowlands. A bit of a ravine (now highway) separates it from another similar hill to the south, and another ravine (now train tracks) separates its western edge from a (possibly artificially) flat area of University of Pittsburgh to the west, to the north and west of which is another hill of similar size. If we figure each of these hills is 3-4 square miles, we can fit six or eight of them in a single "hills" hex, with watercourses, smaller hills, and flat areas in between.
In conclusion, compared to the relative walking range of the average semi-sedentary college student, six-mile hexes are big.
For another point of reference, the portion of Mount Rainier which is permanently snow-covered is about 35 square miles, or a hex and a half. The Wonderland Trail, which forms a ring around Mount Rainier, is 90 miles long; assuming something like 20% backtracking (possibly a bit low), that's about 12 hexes of distance, sufficient to enclose a ring five hexes across (including the hexes containing the trail). Most of the campsites on the trail are between 3000 and 6000 feet of elevation, while the mountain's summit is around 14000 feet of elevation, so there's an average gradient of about 4000 or 5000 feet per six miles within the ring. It looks from the google maps that the foothills radiate another couple of six-mile hexes beyond that ring. Further, it takes most groups who hike Wonderland about ten days, which is fairly close to what ACKS would predict for a heavily-encumbered party on well-maintained trails through hill terrain. The PCs, of course, will be lacking in the trail department, and as a result may also suffer penalties for being in forested terrain in addition to hills...
In conclusion: Mountains are big! I will never again be afraid to take a hexmap and plop down a big zone several hexes across labeled "Mount ???".
Mountains are also useful because you can see them from a long way away. For the sake of simplicity of mental arithmetic, let's say you're looking at a mountain which is 10000 feet taller than you. Sqrt(10k) is 100, plus a negligible amount for your height, times 1.22 means you can see it from 122 miles away, or 20 6-mile hexes (given no other mountains in the way, or, as happens more often in Seattle, atmospheric interference). Obviously you would need to be closer to identify the mountain as Rainier, and not every mountain is as big as Rainier, but if you're in the suburbs of Seattle on a sunny day (ha!) you can use it to get your bearings pretty well. This nicely addresses one of my issues with running a Western Marches-style game where the players don't get to see the hex map - how do you provide meaningful landmarks? There are only so many times I can describe "a peculiar tree" or "a big rock that looks like a thing" before I will start to forget what they mean - single-hex visibility landmarks do not seem like a scalable solution across large numbers of hexes. But big, recognizable mountains, which my players can name... those sound workable.
Aaaand now I want to go hiking.