This, for me, is IQ's masterpiece. Despite the classic The Wake, the revamping of the band that is Dark Matter, or the beautifully crafted new The Road of Bones, Subterranea is this double album with a straightforward concept with fantastic (here meaning "fantasy" and great as well) interplay between all the instruments (bonus for the saxophone) and the amazing lyricism of Peter Nicholls, whose ability to know when to be intense and when to retract still amazes me. This album shines in so many different ways for me that it is really hard to figure out where even to begin with.
I like thinking of Subterranea in terms of Marillion's masterpiece (at least during the Fish era) of Misplaced Childhood: for me, if the concept of Misplaced Childhood was less LSD-ish and had the double of its length, you would kinda get Subterranea. This is only to say how great Subterranea is, for no one would doubt the mastery of Misplaced Childhood.
When the album opens with this tuning orchestra ending with a blast in the first 15 seconds, you know something's coming. Mike Holmes' guitar sets the stage for what's coming, until Provider brings us the angelical (yeah, angelical) voice of Nicholls, which is a lot different than your usual vocals. Now, when the title track of Subterranea strikes, you start to realize you're in for something big. Then, when you get the sax, you're sure of it. You don't even see you've hit the end of the fourth song of Sleepless Incidental until it happens! The rest of the first disc is full of those great perks as well, and it follows until it hits The Sense in Sanity, this quasi-acoustic song that goes through seven minutes of heart-wrenching vocals. To top it of, State of Mine introduces the album's greatest theme in my opinion, with this 007 feeling. This theme is revisited right in the first seconds of the second disc, so you imagine how I feel about that. The second disc is way more atmospheric, more of a character-questioning album, and could easily be perceived as a drama-action OST. This is my favorite stretch of music of the whole piece for me: from State of Mine to High Waters. It's all paired so well, so you have the interludes to breathe and soak in what you heard, but not too long for it to feel overtimed. In the end, you get the 20-minute epic of The Narrow Margin, and I'll admit this fell short for me in the first 10 listens of the album or so. This is a song that grows on you over time, and once you realize the album themes it reintroduces, or how it wraps up the album's concept so well, your feelings towards it change. For me, it's an epic that just feels like a couple of songs mashed up together, in the sense that I don't get the epic feeling of it, but it's a good 3-4 songs joined together nonetheless.
Having talked about the album, I have to talk about the concept. This is based on Kaspar Hauser, this German kid who had claimed to have grown up in captivity back in 1828, deprived of any sensorial experiences, only being fed through a small opening on the door of the place. IQ turned it into a person that grows in the same conditions and is released (or escaped, it's not clear). That person faces a lot of experiences and sensations never felt before. A lot (like, a lot) of stuff happens, and I won't explain that here because it ruins the fun, and how the story ends is the perfect definition of "surprising, but not unexpected". It's really fun and neat to try to figure out the story for yourself, and I totally recommend.
Personally, all of that raised some questions about my personal life, and this was stuff I needed. So, I have a deep personal connection to this album. Very little music has had such an impact on me, and I can't not rate it 10/10. It is a really underrated masterpiece, whose logo of the experiment the main character is in I want to get tattooed. These aren't bold claims, they're just what the album is. Give it a spin, it will not disappoint you.