Just found my way into Blackreach, which has become the favourite section of Skyrim I have since encountered. For one it is so fucking massive, it can take a whole hour or more to search the entire cavern. And it also has fucking gigantic bio-luminescent mushrooms coming from the ground and ceiling. When I first found this place and ended up out up of the opposite side of the map, I immediately thought of the adventure of Professor Lidenbrock and Axel from Journey to the Centre of the Earth where they explored a cavern, the entrance of which was in an extinct volcano, and they ended up in Italy, ejected from a live volcano by the end of the story.