77. Rosetta - The Galilean Satellites (2005)
I've written about this album before in my 101 Albums... thread so this will be more of a summation of that particular post (you can read the full thing
here).
This is easily one of the most ambitious debuts of a band I have ever had the fortune to hear. Essentially it's a double album, with one disc being the harder metal, and the other being ambient noise. When you sync bother albums you get an incredibly heavy and atmospheric album that really feels crushing with the right headphones. The "Post-Metal" term is pretty nebulous, and this band in particular have not endorsed it or considered themselves to fall under the umbrella, however sometimes people have a way of making things stick, and enough people in the metal community have tried there hardest to make it a real genre label. Whatever you want to call it, if you like sludgey metal with a deep wall of sound and lyrics about exploring the cosmos, Rosetta's debut album definitely deserves your attention.