I've recently gotten back into first edition D&D (AD&D) and had overlooked for years that there's a whole dungeon generation "algorithm" in the back of the book. I've started to use it to play "solitaire", which I've learned is a fairly popular thing to do for old DMs that enjoy practicing their DM skills (you roll up your own group and pretend they're making their own choices). What's fun about it is that the dungeons it generates are crazy. Diagonal passageways, varying passage widths, stairways that might go down multiple levels and then come back up, rooms that are only accessible by traveling to other levels temporarily, etc.

The other thing that is interesting is that the order of generation is based off the party's choice of what door/passage to explore next, so it's very much intended to be generated during actual play.

I've thought more than once it would be fun to work up a tool to generate that dungeon on demand, to just press a button each time a choice is made and then watch it animate.