One of the Bioware Neverwinter Nights expansions was to go inside some mega dungeon that I know existed in the lore from reading the FR DM guide with all the history and such; but I can’t remember what original module it was taken from. IIRC, the dungeon was made by Elminster? I just remember recognizing the name and then being kinda disappointed with it because in NWN it’s not quite as big as I had imagined. lol