A real dungeon!
Many sheets of graph paper have been covered with tunnels, depicting shrines, tombs and other kinds of underground complexes. One very good rationale for underground tunnels is of course mines. Now have I finally been down into a real, dark and muddy mine and thought about sharing some of my impressions. Maybe you have read the Dungeon survival guide that TSR put out for 1st ed, and think that was good enough, or just not the territory you wanted to take your game. I'm not going to try to cover that territory again, instead trying to focus on my feelings and impressions of mines as an environment, which might give some idea what you waht to do with underground complexes in your game as far as general feel is concerned.
The first thing I was thinking about when I stood in a small steel cage that was rushing down into the depths of the earths was how claustrophobic it felt. It was also a very , very quick elevator. I don't think I've ever travelled an elevator at such a breakneck pace before. That will of course be of relevance for a gaming situation. How will you enter the underground? It's probably very far deep down, and that whole in the ground is probably not made for comfort, but for some other purpose (like hauling ore).
When I first stepped out of that metal cage, two things struck me. The noise down there, and the heat. Now, most people thing of the underground as cool and wet. While the latter might be true up to a certain depth, depending on the kind of rock, the fact that a mine actually gets hotter as you go down is maybe not that obvious. If your dungeon is a mine, where people actually dig after ore, I think it might give a better impression of realism if your delvers will find either creatures equipped for handling extremely hot working conditions either by technology or my natural abilities. The mine I visited was ventilated and had cooling equipment, but it was still very hot. The natural ambient temperature was 42 degrees, Celsius! I was told that gold mines in South Africa are as hot as 60 degrees. Murderous environment!
The noise then. In a modern mine there are fans, cooling radiators, ducts of cool and warm air that flows in the tunnels. I have no idea how they did that back in the bad old days, but the wind can, if you end up in the wrong tunnel not only blow you off your feet, but also been scorchingly hot or maybe bring with it dust and sand which will be just as bad as end up in a sandstorm in a desert.
Those hazards brings me to another topic. When I draw dungeons, they very often end up far to regular. I've written about that before, how my dungeons look way to much like the downtown road network of a north American metropolis if I'm not careful. In a mine, or any other kind of underground, there will be hazards galore. Especially if there's monsters fair an foul wandering around. So, there's probably a lot of small niches, dead ends or other short tunnels and alcoves only used for hiding when something nasty comes down the tunnels. Make sure you include some of them in your own dungeons, I sure will do in the future.
I know I've read many times about how classic old school dungeons might have signs or chalk markings left by former delvers or inhabitants. That is also something that was very obviously present in the mine I went down into. If there was a compressor for the air vents, it was labelled. Also, big grey housings for the electricity down there was labelled Danger and “13800 Volts” and similar. “Foul Air, beware” was another one. Apart from signs there was also a lot of chalk markings, mostly numbers and arrows. This of course brings home the fact that many of the signs down below will only make sense for the intended recipient. Some might be general warnings, and other might be very cryptic. Obvious usage of that kind of things is to give players a hint of the friendliness of the inhabitants of an area. Are they expecting traffic, and someone who might need guidance? This is an area where I see intelligent delvers succeeding where foolhardy ones might not. Make sure you see the signs, subtle and obvious, and act accordingly.
A few more things struck me as interesting down there. Since the air, even when the whooshing air fans had brought it down, was a bit stale and it was tiring to walk far when the air was more saturated with CO2 and has less oxygen that usual. Also, the amount of muck and mud down there was amazing. The idea of bringing a spell book down there boggles the mind! It's very dry 6800 feet down, since it's below the ground water, but the dust is there. And when you have water, there's mud everywhere! It might not be fun to consider all the details like humidity, sulphurus air, dust and what effects they have on swords, leather and spell books. But, make sure you tell your delvers that they look like they have been crawling in mud, or that they are dusty and dirty. They might get some of those utility spells that way, and will feel at least a tiny bit more real.
A mine is a very moody setting for adventure, and a very different environment. It's very deadly, very confined, very hot and very mucky. And loud noises everywhere from wind or equipment. It's wrap up with a short atmospheric piece. As I was going along one of the big tunnels, I passed a smaller side passage, and turned my helmet lamp in that direction to see what it was. There it was, a small tunnel, with uneven floor and with very varying height so would have to stoop down to just get through. Far up ahead I saw a fork in the road, where the tunnels moved on, smaller and smaller, and a rusty chain hanging across one of the passages with a sign sayign “Beware” and the rest illegible. A maze or twisty passages, indeed. I went on following the main tunnels.