Yesterday, I discovered that my stationery cupboard at work has a huge stash of A1 notepads. Of course, work stationery exists only to be pilfered, so I will help myself to one sooner or later, but a great idea (great to me, at any rate) popped into my head as well the moment I saw them: megadungeons on A1 scrolls.
I have experimented in the past with mapping dungeons on A3 paper because it allows you to easily include both map and key on the same page (the latter either situated in a box in a corner or as notes within/next to rooms), with space to breathe, cutting out the need to flip between pages or files. How much truer would this be of A1 paper? Especially if the whole thing (or at least an entire, sprawling level) could be made to fit on one sheet. If so, it would be a simple matter to carry round a megadungeon rolled up in a tube, whether as one sheet or several. Pop a sheet of house rules in with them, and you're ready to go. The advantage of the scroll is also that one does not need to unwind the whole thing - just the cross section where the action is happening.
I would much prefer to run a dungeon from a scroll than from a book, if only for the vibe, man.