Areadnie wasn't too intimidating, the dreadnought was a baby's thing.
Causeways were really intensifying, and who can forget the dreaded corridoor of blades? only some dungeoneers survived that.
From earlier series the bomb rooms were farily intense and, perhaps my favourite room, was the dread medusa, now that was intensity and a half as dungeoneers would freeze if they were not careful, and you never knew whether they were being careful or not.
Oh, and of course, the trolls - when you heard those footsteps get louder, it alll got so intensifying and thrilling.