In ages past the gigantic, multi-level dungeon was seen by many as the core of an ongoing campaign. Surrounding wilderness and towns were more like additional hazards and resupply points than destinations in their own right. This very site found fame through the adventures recording in The World's Largest Dungeon, and with the OSR (Old School Renaissance) movement "megadungeons" found a new and enthusiastic audience (or at least an old audience with renewed enthusiasm).
Earlier this evening I noticed that the troubled Dwimmermount project had finally been released: here's a link to the Labyrinth Lord version. Tempting though it is to pick that up - and the PDF is at a pretty fair price - I rather doubt I'll ever do much with it if I do. Most of my early fantasy gaming was in cities, and aside from a few very short forays underground it's only quite recently that I've done much with dungeon adventures; I'm really not sure I could sustain an underground campaign.
Do you have any thoughts on megadungeons? A particular favourite, perhaps, or a desire to hear a certain one explored on RPGMP3? Would you rather they were consigned to the Biffa bin of history?