I didn’t use the term “nodes”, which might be better than the “megamodules” I was talking about once… and the dungeons in between my nodes/megamodules were more like small waypoints, which is not what I think either JD or Beedo are getting at. I think they are not talking about long underground features – great chasms, mile-long tunnels, underground rivers – with 1 to 3 tiny dungeons along the way. I think they mean more like a solid maze of tunnels extending for miles, with the entire maze being treated as a hexcrawl, only describing individual tunnels as needed. Something like: “The goblin king tells you that if you travel through the Great Rift, you will eventually reach the Obsidian Gate to the kingdom of trolls”. And along the way, you mention many caves in the sides of the Great Chasm, but don’t map out or describe them unless the players pick a random cave to explore or make camp in.
What I think might be applicable here is to use the urban crawl rules from Vornheim. Put your nodes on the big sketchmap first, then draw lines connecting the nodes. Each line represents one route through a maze of twisty passages, all alike. On one side of a line/route, write out numbers from one to six, one to ten, or one to twelve, whatever fits, in an arbitrary order, as you would for neighborhoods. Do the same for the other side of the line: you can either repeat the numbers in a different order, so that you can have a Three East and Three West, for example, or split numbers between the two sides without repeating “neighborhoods”. So, you have something like:
X I VE THREE S ONE FI _______________ FOUR TWO
… But with the letters butting up against each other, so that they connect.
On the outside of these “neighborhoods”, use a second set of words from a short descriptive phrase, like “UNDEAD WORM PITS”. This becomes a quick description of that area on the map and a rough guide to the major routes through that area. When crawling through a given “neighborhood”, use numerals for individual tunnels, the way Zak uses them for street-by-street paths through a neighborhood. You don’t need to map the individual tunnels at all, until the players decide to explore or are forced to escape into unknown areas.