Dang, to be honest the dungeons started to blend together in Skyrim. Nord dungeons and Dwarven dungeons. Either a single area or a three tier area. Not much
But yes, Blackreach was very pretty (just learned that you can blast the ball to summon the dragon). Although Falmers were a piece of cake thanks to the fact that my sneak was out the wazoo.
They did blend and got very repetitive, but it was still a big improvement over Oblivion's dungeons. In Oblivion I pretty much ignored them after a while.
The ones with the large caves with waterfalls and Dwemer structures were great. But unfortunately there were also tons of seen it all before caves and dungeons where you could see all the standard building templates stick out like a sore thumb.