I have explored many dungeons with my lvl. 18 dark elf and came across some really big dungeons (I'm currently in "The Cavern of Homunateusia" in Sentinel - quite large). And for now I can say: The bigger the dungeon, the more fun
So what are the biggest dungeons you have explored? How big was the yellow mini map (which roughly shows the size)?

the largest dungeon ive played was an orc stronghold. Due to a glitch (big surprise ) the dungeon was endless. every door would lead to the same 5 rooms with no quest item in sight.