I honestly had to put the pad down when I entered blackreach, what a sight to behold... it was like stepping onto an alien planet. I couldnt even see the roof of that cave.
I love how the dwemer have a sort of atlantis vibe in skyrim.
Blackreach was great. It recaptured the feeling I had when walking into Sadrith Mora for the first time in Morrowind; or exploring Mania for the first time at night in the Shivering Isles.
Spoiler
Like many others, I forgot the lexicon, so I have to go back at some point.